In our school over here in the UK, we like to ask the children about their current understanding (sometimes at the start, sometimes during and sometimes at the end of lessons). We use traffic light colours to do this. I have added a red dot next to the A, an orange dot next to the B, a green dot next to the C and a white dot next to D. Red normally means limited understanding and need help, amber is getting there, green means they have understood it and white is expert meaning they could teach it someone else. It has been very useful to have a snapshot of the classes understanding at the end of a lesson to inform my planning for subsequent lessons! Before, the children showed me their understanding using a traffic light slider but I would often forget who had shown what. A great app.