“I really hate it when teachers say things like: ‘You should know this’ or ‘This is Year Seven work’ or ‘This was in your KS3 textbook you should have learnt this.’ It makes me feel even more pathetic than I already am…Thanks!” (from a Yr 9 focus group student). This session will explore the benefits of recognising and living with the inherent complexity and tensions of classroom teaching – as captured in this common moment. What is a ‘you should know this’ moment? Why are they so common? What do they suggest about the complexity of teaching? What are the practical implications?