Sixth Form students recently gave us some feedback on their progress in lessons. This led to work on models of significant progress and these four possibilities: 1) A substantial component of a linear course is developed with a clear step towards a final goal. 2) One (possibly small) element of the course is taken from minimal knowledge to complete understanding at a high level. 3) A key conceptual barrier is overcome so that a new area of work can be accessed. 4) A definite upward shift of knowledge / understanding / skill is taken by choice by students, aided by prompts or questions. We would be interested in any views of our analysis, especially for the purpose of defining progress within observed lessons.