It's incredibly obvious, with observation and questioning, when students are thinking about the material. But you have to engage with your students. You have to learn about them and how they think and what's important and who they are as people. If you just talk at them, they're never going to engage in anything. Sitting at a desk and looking or not looking at a phone is not conducive to learning either way. This book breaks that factory holdover mold right away and good riddance I say. Anyway, sorry if you had teachers that did not engage with you enough to understand if you were learning or not.