It sounds disingenuous to say but the truth is that teaching two, three, four and five year olds is a lot like training a pet. They need to be disciplined. This involves praise when behavior is in accord with what is desired and correction when it is not. I give out plenty of high-fives and stickers when kids get it right and take extra time one-on-one with the slower kids. When the children start to mess around, pick their nose, talk to other kids, etc. I will do something like make them stand in the place and take their chair for a few minutes (As I said before how the chair is of great importance to the kids).