SOLO (Structure of Observed Learning Outcomes) is a model that helps teachers and students understand the learning process through a common language. It describes five levels of understanding - prestructural, unistructural, multistructural, relational, and extended abstract - that represent increasing complexity in learning from surface to deep understanding. SOLO provides a simple framework for assessing student work, giving feedback, and pushing learning to a deeper level. When implemented school-wide, it can help students recognize their own progress in learning across subjects.