"The SOLO taxonomy is a model that describes levels of increasing complexity in students’ thinking and understanding. It was proposed by academics Biggs and Collis (1982) after classifying student’s thinking across a range of ages and a range of subjects. As thinking progresses across the levels, students move from factual, knowledge-based thinking to conceptual and abstract thinking and understanding.

Lynn Erickson’s Structure of knowledge (2002) is often used to illustrate how concepts and knowledge interact to help students form a principal generalization (similar to the “central ideas” in programmes of inquiry in the Primary Years Programme (PYP)). The foundations of being able to form these principal generalizations (or to think conceptually and understand a PYP central idea) are based on acquiring “essential” knowledge that will interact with chosen key and related concepts.

The SOLO taxonomy supports Erickson’s “structure of knowledge” as it starts with students collecting ideas, facts or knowledge before progressing to more sophisticated and demanding levels of thinking where they are required to process the information to make connections, conceptualize and transfer their understanding."