SOLO Taxonomy: Five Levels of Understanding Explained
SOLO taxonomy explained: five levels from prestructural to extended abstract. How to design learning outcomes and assessments that track visible pupil progress.
What is the SOLO taxonomy?
SOLO taxonomy (Structure of the Observed Learning Outcome) is a framework developed by Biggs and Collis in 1982 that classifies the quality of a learner's response into five levels: prestructural, unistructural, multistructural, relational, and extended abstract. Unlike Bloom's taxonomy, which classifies the task, SOLO classifies the response itself, making it a powerful tool for formative assessment and helping learners understand what makes an answer superficial or deep.
As a teacher, you want practical ways to assess and develop your students' depth of understanding, and SOLO Taxonomy provides exactly that framework. This structured approach helps you identify where each learner sits across five distinct levels of comprehension, from basic recall through to sophisticated analysis and creative application. Rather than simply marking work as right or wrong, SOLO Taxonomy enables you to guide students through a clear progression of thinking skills whilst building their metacognitive awareness. The real power lies not just in understanding the five levels, but in knowing how to use specific classroom
Key Takeaways
- SOLO Taxonomy fundamentally shifts the focus of assessment from the quantity of information recalled to the quality and depth of learners' understanding. This structured framework, developed by Biggs and Collis (1982), provides teachers with a clear progression of cognitive complexity, enabling them to precisely identify where a learner's learning sits and how to scaffold their process towards deeper conceptualisation. It moves beyond simple right or wrong answers, offering a nuanced view of learning.
- Implementing SOLO Taxonomy equips learners to become metacognitively aware learners, taking ownership of their intellectual development. By making the five levels of understanding explicit, teachers provide learners with a common language to articulate their learning progress and identify next steps, as highlighted by Hook and McRae (2011). This clarity fosters self-assessment and encourages learners to actively strive for higher-order thinking.
- SOLO Taxonomy offers a robust and versatile framework for differentiating instruction and assessment across all subject areas. Its hierarchical structure allows educators to design tasks and provide feedback that precisely matches learners' current understanding, guiding them from surface-level engagement to profound, interconnected knowledge (Biggs, 2003). This adaptability supports inclusive teaching practices and targeted intervention.
- Developing learners' capacity to reach the Relational and Extended Abstract levels is crucial for cultivating genuine expertise and critical thinking skills. Teachers can utilise SOLO to challenge learners to make meaningful connections between ideas, analyse complex relationships, and creatively apply knowledge to novel situations (Biggs & Collis, 1982). This progression fosters sophisticated problem-solving abilities and a transferable understanding of concepts.
SOLO Taxonomy was developed by John Biggs and Kevin Collis, two educational researchers who were interested in creating a framework that could help teachers design more effective classroom activities. The framework is based on the idea that there are different levels of understanding, and that students can move through these levels by engaging with increasingly complex tasks and ideas. By using SOLO Taxonomy, teachers can create lessons that are tailored to each student's current level of understanding, and that help them progress towards more sophisticated levels of knowledge (Sumagaysay & Valdez, 2025).
SOLO Taxonomy is often used in conjunction with the concept of constructive alignment, which is the idea that learning outcomes, teaching activities, and assessment tasks should all be aligned with one another. By aligning these three elements, teachers can ensure that their students are learning in a way that is both meaningful and effective.
With SOLO Taxonomy, teachers can design activities that are aligned with the specific level of understanding that each student has already achieved, and that help them progress towards more advanced levels of understanding. This approach allows students to build on their existing knowledge and skills, and to develop a
Why Use SOLO Taxonomy in Education?
SOLO Taxonomy enhances student learning by providing a clear framework that shows students exactly where they are in their understanding and what steps they need to take next. Teachers can use the five SOLO levels to create tailored lessons that match each student's current understanding level and guide them towards more sophisticated thinking (Tusoy & Baraquia, 2025). This approach helps students move beyond memorisation to develop genuine comprehension and critical thinking skills.
Solo Taxonomy is a systematic way that describes how learners' understanding build from easy to difficult while learning different tasks or subjects. The Solo Taxonomy can be used to enhance the quality of learning within the classroom teaching and provide a systematic way of developing deep understanding (Damopolii, 2020). Student learning can be guided in ways that promote deep learning, much like how scaffolding supports learners through the zone of proximal development.
SOLO Taxonomy is a valuable tool for assessing the depth of knowledge that students have achieved in a particular subject or task (Chen & Nunes, 2025). It allows teachers to identify where students are in their learning process and determine what steps need to be taken to move them to a deeper level of understanding.
By using SOLO Taxonomy, teachers can design activities that are appropriate for each student's level of understanding and encourage them to move towards deeper levels of knowledge. This approach works similarly to differentiation strategies and can lead to a more effective and engaging learning experience for students, and ultimately, better academic performance.
The Origins of SOLO Taxonomy: Biggs and Collis (1982)
SOLO Taxonomy was published by John Biggs and Kevin Collis in their 1982 book Evaluating the Quality of Learning: The SOLO Taxonomy, and its development drew directly on Jean Piaget's stage theory of cognitive development. Biggs and Collis observed that students' responses to academic tasks did not simply become more numerous with age , they became structurally different in kind, progressing from fragmented, disconnected responses through to generalisable, abstract understanding (Biggs & Collis, 1982). This structural approach to learning quality distinguished SOLO from earlier taxonomies that focussed primarily on knowledge content rather than on the observable architecture of student thinking.
The acronym SOLO , Structure of Observed Learning Outcome , is significant. Biggs and Collis were deliberate in anchoring the taxonomy to what teachers can actually observe and evaluate in student products, whether written responses, verbal explanations, or practical demonstrations. This observational grounding gives SOLO a practical advantage over frameworks that depend on inferring unobservable mental states. Where Piaget's stages described developmental ceilings, SOLO described task-specific levels: a student operating at the Relational level in geography might simultaneously remain at the Unistructural level in a new mathematics unit, depending on their prior knowledge (Biggs, 1999).
Biggs later connected SOLO directly to his theory of constructive alignment, arguing that learning outcomes, teaching activities, and assessment tasks should all be calibrated to the same SOLO level (Biggs & Tang, 2011). A learning outcome written at the Relational level , for example, "explain how climate change affects biodiversity" , requires assessment tasks and teaching sequences that genuinely demand relational thinking, not merely the recall of isolated facts. When all three elements align, students receive a coherent signal about the depth of understanding expected, which improves both attainment and metacognitive awareness.
The Five SOLO Levels Explained
The Structure of Observed Learning Outcome, presents a compelling way to structure the complexity and quality of students' thinking into distinct levels. Unlike Bloom's hierarchical approach, it's a versatile tool that allows educators to gauge attainment levels and encourage quality learning. This taxonomy consists of five levels, each representing a different depth of knowledge and ability level.
- Prestructural Level: Here, students exhibit a lack of understanding, often missing the point entirely. The level of thinking is minimal, with a focus more on lower-order verbs such as identify, memorise, and recall. This limited processing may be due to cognitive load overwhelming the student's working memory. It's the first stepping stone, a difficulty level that needs overcoming before progressing.
- Unistructural Level: At this stage, students can identify singular aspects of knowledge, and their understanding is limited to isolated disciplinary knowledge. For instance, a student might identify that water boils at 100 degrees Celsius but may not understand why this happens. This level shows the beginning of schema formation.
- Multistructural Level: The quantity of knowledge increases at this level. Students begin to gather multiple pieces of information, but they struggle to relate them coherently. For example, a student in this stage might know the boiling point of water and that heat energy is involved, yet fail to link these facts.
- Relational Level: This is where the magic of student-led learning starts to manifest. Students begin to connect the multistructural elements into a coherent whole. Their level of thinking becomes more complex, and they start to understand the relationships between facts. This connects well with inquiry-based learning approaches and classroom dialogue. For instance, a student at this level would understand that water boils at 100 degrees Celsius due to the increased kinetic energy of water molecules.
- Extended Abstract Level: The zenith of understanding, where students can generalise beyond the given context and apply their knowledge to new, abstract situations. At this level, students demonstrate the highest quality of learning, showing creative and effective thinking. They can take their relational understanding and extend it to hypothetical scenarios or different contexts entirely. For example, a student might understand not only why water boils at 100 degrees Celsius but also predict how altitude or atmospheric pressure would affect this process, or apply these principles to other substances.
Each level builds upon the previous one, creating a natural progression that teachers can use to design learning activities and assess student understanding (Jørgensen et al., 2024). The beauty of SOLO Taxonomy lies in its ability to show what students know and how they can use that knowledge to think and reason.
Understanding these five levels allows teachers to identify precisely where each student sits in their learning process and design targeted interventions to help them progress. Unlike traditional assessment approaches that might simply mark answers as right or wrong, SOLO Taxonomy reveals the quality of thinking behind student responses.
SOLO Taxonomy and Bloom's Taxonomy: Understanding the Difference
SOLO Taxonomy and Bloom's Taxonomy are the two frameworks teachers most frequently encounter when designing assessment and questioning sequences, and understanding how they differ helps clarify when each is most useful. Bloom's Revised Taxonomy (Anderson & Krathwohl, 2001) organises cognitive processes into six hierarchical categories , Remember, Understand, Apply, Analyse, Evaluate, Create , and focuses primarily on the type of mental operation a learner is asked to perform. SOLO Taxonomy, by contrast, focuses on the observable quality and structural complexity of the student's response, regardless of which cognitive process produced it. A student can apply knowledge whilst remaining at the Multistructural level if that application involves executing disconnected procedures without integrating them into a coherent understanding (Hattie & Purdie, 1998).
This distinction has practical implications for lesson planning. Bloom's Taxonomy is particularly well suited to curriculum mapping, because its six categories provide a vocabulary for specifying the type of cognitive challenge embedded in a learning objective , teachers can ask whether a unit emphasises recall-level tasks or whether it pushes students towards evaluation and creation. SOLO Taxonomy is typically more useful for in-lesson formative assessment, because it describes the quality of an individual student's current response and points directly towards the next step. A teacher observing that a student's written explanation lists multiple facts without connecting them can immediately identify the response as Multistructural and ask a bridging question designed to prompt relational thinking, such as "How do those three ideas work together?" This immediate diagnostic function is less readily available in Bloom's framework (Biggs & Tang, 2011).
Many teachers find that the two frameworks complement rather than compete with each other. A useful working principle is to use Bloom's Taxonomy when writing learning objectives and scheme-of-work plans , because it maps cognitive processes across a curriculum sequence , and to use SOLO Taxonomy when writing rubrics and designing the questions within an individual lesson. Biggs and Tang (2011) advocate explicitly writing SOLO-aligned intended learning outcomes, then selecting teaching and assessment activities that require students to demonstrate the targeted SOLO level. Bloom's language ("students will be able to analyse...") can sit alongside SOLO language ("a response at the Relational level will...") without contradiction; they describe different aspects of the same learning process.
SOLO Taxonomy Classroom Implementation Guide
Teachers can implement SOLO Taxonomy by using the five levels to design learning activities, create assessment rubrics, and provide targeted feedback. Start by identifying which SOLO level your learning objectives target, then design activities that scaffold students through each level systematically. Use SOLO-based questioning techniques and rubrics to assess student understanding and guide them towards deeper thinking.
The practical implementation of SOLO Taxonomy begins with lesson planning. Teachers should design activities that deliberately move students through the levels, starting with tasks that help them grasp single concepts (unistructural) before progressing to activities that require them to handle multiple pieces of information (multistructural). This might involve retrieval practise activities at the lower levels and more complex problem-based learning tasks at higher levels.
Assessment becomes more meaningful when structured around SOLO levels. Rather than simply checking for correct answers, teachers can evaluate the sophistication of student thinking (Diana, 2020). A student might give a partially correct answer but demonstrate relational thinking, which provides valuable insight into their understanding and suggests specific next steps for learning.
Creating SOLO-based rubrics transforms both teaching and learning. These rubrics make expectations explicit for students whilst providing teachers with a systematic way to evaluate student achievement. Students can use these rubrics for self-assessment, helping them understand what deeper thinking looks like in practise. This approach supports the development of metacognitive skills as students become more aware of their own thinking processes.
Questioning strategies should also reflect SOLO levels. Teachers can design question sequences that gradually increase in cognitive demand, moving from simple recall questions through to extended abstract applications. This systematic approach to questioning helps ensure that all students are challenged appropriately whilst being supported to reach higher levels of understanding.
SOLO Taxonomy Verbs: Designing Questions and Tasks at Each Level
One of the most practical applications of SOLO Taxonomy in daily teaching is the use of level-specific verbs to frame questions, tasks, and success criteria. Biggs and Collis (1982) identified that each level of the taxonomy is associated with characteristic cognitive operations, and selecting verbs that match those operations ensures that the cognitive demand of an activity aligns with the intended learning outcome. Using SOLO verbs removes ambiguity from rubrics and helps students understand precisely what quality of response is expected.
At the Prestructural level, verbs such as misidentify, tautologise, and miss the point describe the type of response a student produces, which is useful diagnostically but not productive as a task verb. Teachers use this level primarily as a baseline indicator rather than as a target. At the Unistructural level, appropriate task verbs include identify, name, define, follow a simple procedure, and recall one relevant fact. A history teacher might ask: "Name one cause of the First World War." At the Multistructural level, verbs shift to describe, list, enumerate, classify, and outline several features. The same history teacher might ask: "Describe three causes of the First World War" , a task that requires more information but does not yet demand that students connect those causes into a coherent explanation (Hook & Mills, 2011).
The cognitive step change appears at the Relational level, where verbs include explain, compare, contrast, analyse, apply to a known situation, argue, and justify. Here, students must integrate multiple pieces of information into a coherent account: "Explain how the three causes you described were interconnected." At the Extended Abstract level, verbs move to theorise, hypothesise, generalise, reflect, create, and evaluate across contexts. An Extended Abstract question might ask: "How far does the concept of nationalism as a cause of conflict apply to twentieth-century wars beyond the First World War?" Sequencing questions through these verb levels within a single lesson creates a structured progression from retrieval through to genuinely transferable reasoning, and students who can see this progression become more self-directed in targeting their own next level (Hook & Mills, 2011).
SOLO Taxonomy Assessment Strategies
SOLO Taxonomy offers teachers a powerful lens through which to view student learning and understanding. By moving beyond surface-level assessment to examine the quality and structure of student thinking, this framework enables more precise and effective teaching interventions. The five levels provide a roadmap for both teachers and students, making the process from superficial understanding to deep, transferable knowledge both visible and achievable.
The strength of SOLO Taxonomy lies in its assessment capabilities and in its potential to transform classroom practise. When teachers design lessons with SOLO levels in mind, they create learning experiences that systematically develop student thinking. This approach ensures that students don't just accumulate facts, but develop the cognitive structures necessary for genuine understanding and creative application of knowledge.
As education continues to evolve towards developing critical thinking and problem-solving skills, frameworks like SOLO Taxonomy become increasingly valuable. They provide the scaffolding necessary to support both teachers and students in the complex process of deep learning, ensuring that educational outcomes reflect what students can remember and what they can actually do with their knowledge.
Criticisms and Limitations of SOLO Taxonomy
SOLO Taxonomy has attracted substantial support in educational research, but it has also been subject to a range of criticisms that teachers should understand before adopting the framework. The most frequently raised concern is the assumption of linearity: SOLO implies that students progress through the five levels in a fixed sequence, from Prestructural through to Extended Abstract. Critics point out that this sequential model does not always reflect how learning actually unfolds, particularly in domains where novice learners may produce Extended Abstract-style speculation before they have secured the foundational Unistructural knowledge that gives those ideas genuine meaning (Hattie & Purdie, 1998). In practice, a student who has been taught to produce the surface features of Relational writing , for example, by using connective sentence starters such as "this is because" , may receive a higher SOLO level score without having developed the conceptual integration the level is intended to capture.
A second criticism concerns subject-specificity. Biggs and Collis (1982) acknowledged that the SOLO levels manifest differently across disciplines and that what counts as Extended Abstract thinking in mathematics , where a student generalises a pattern across number systems , is structurally different from Extended Abstract thinking in English literature, where a student relates a text's themes to broader cultural or historical contexts. Critics argue that the framework is too generic to capture these disciplinary differences without significant adaptation, and that applying a single SOLO rubric across subjects risks rewarding the formal appearance of connection-making rather than the substantive quality of disciplinary reasoning (Marzano & Kendall, 2007). Teachers working across departments may find that the level descriptors require extensive subject-specific exemplification before they can function as reliable assessment tools.
Questions have also been raised about cultural and linguistic factors. SOLO Taxonomy, like most Western educational frameworks, privileges the ability to produce extended written or verbal explanations of conceptual relationships , the very forms of expression that are central to academic discourse in anglophone schooling systems. Research conducted in East Asian contexts, where rote learning and memorisation have traditionally served as foundations for subsequent deep understanding, suggests that the SOLO hierarchy does not straightforwardly translate across pedagogical traditions (Watkins & Biggs, 2001). Students who perform complex relational thinking through non-verbal means, or who express understanding through disciplinary practices less legible to a Western observer, may be underestimated by standard SOLO assessments. None of these limitations invalidates SOLO Taxonomy as a classroom tool, but they do caution against treating any single SOLO score as a complete or unbiased account of a student's understanding.
Frequently Asked Questions
How long does it take to implement SOLO Taxonomy in my classroom?
Most teachers can begin using basic SOLO Taxonomy principles within 2-3 weeks of learning the framework. Start by applying the five levels to one subject area or lesson type first, then gradually expand to other areas. Full implementation across all teaching practices typically takes a term to develop confidence and see consistent results.
Can SOLO Taxonomy be used with primary school children?
Yes, SOLO Taxonomy works effectively with primary learners when adapted with age-appropriate language and visual aids. Young learners can understand concepts like 'one idea' versus 'connecting ideas' when presented through simple symbols or colours. The framework helps primary teachers scaffold learning progressively and identify exactly where each child needs support.
What's the difference between SOLO Taxonomy and Bloom's Taxonomy for lesson planning?
SOLO Taxonomy focuses on the structure and complexity of student responses, whilst Bloom's emphasises cognitive processes like remembering or analysing. SOLO is particularly useful for designing questions that reveal how well students can connect and extend ideas. Many teachers find SOLO more practical for day-to-day assessment because it shows the quality of understanding rather than just the type of thinking skill used.
How do I create SOLO Taxonomy rubrics for different subjects?
Start by identifying what 'one idea', 'several ideas', 'connected ideas', 'extended ideas', and 'abstract ideas' look like in your specific subject. For example, in history, this might progress from stating one fact, to listing several facts, to explaining cause and effect, to comparing different periods. Create subject-specific language and examples for each level to make rubrics meaningful for your students.
Is SOLO Taxonomy suitable for students with special educational needs?
SOLO Taxonomy is particularly beneficial for SEN students as it clearly shows small steps of progress and celebrates different levels of understanding. The framework helps teachers set realistic targets and recognise achievement at any level rather than expecting all students to reach the same endpoint. Visual representations of the five levels can be especially helpful for students who struggle with abstract concepts.
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Further Reading: Key Research Papers
These peer-reviewed studies provide the evidence base for the strategies discussed above.
Evaluating students’ computation skills in learning amount of substance based on SOLO taxonomy in secondary schools View study ↗
Tian et al. (2024)
This study demonstrates how SOLO taxonomy can assess students' computational skills in chemistry, particularly with challenging concepts like 'Amount of Substance'. Teachers can use this framework to identify different levels of student understanding and design targeted interventions for secondary chemistry learners.
What Is Hard about Teaching Machine Learning to Non-Majors? Insights from Classifying Instructors’ Learning Goals View study ↗
54 citations
Sulmont et al. (2019)
Whilst this paper focuses on machine learning education, it highlights the importance of classifying learning goals using structured frameworks. Teachers can apply similar taxonomic approaches to clarify objectives and assess student progress in any subject requiring complex skill development.
Learner’s Diagnostic Achievement and Teacher’s Readiness Towards Solo Taxonomy-Based Learning Guide in Chemistry View study ↗
Sumagaysay et al. (2025)
This research examines teacher readiness for implementing SOLO taxonomy-based learning guides in chemistry education. It emphasises how collaborative learning approaches can enhance conceptual understanding, providing teachers with evidence-
The Use of PhET Simulations in Evaluating Students’ Level of Cognitive Skills Utilising Solo Taxonomy View study ↗
Tusoy et al. (2025)
This study shows how PhET simulations combined with SOLO taxonomy can evaluate students' cognitive skills in science. Teachers can use this digital approach to assess different levels of student understanding whilst incorporating engaging technology into their science lessons.
An LLM-Based Framework for Simulating, Classifying, and Correcting Students' Programming Knowledge with the SOLO Taxonomy View study ↗
Zhang et al. (2025)
This research develops an AI framework using SOLO taxonomy to assess programming knowledge and provide feedback to students. Teachers can understand how structured taxonomies help identify student misconceptions and guide appropriate support strategies in computational thinking subjects.
