Don't worry. You can leave it to the teacher and they will have their own method to teach the kids. Of course you can try to play flash cards, singing or borrow some books from library and read together with him. My son is now studying K3 at a local kindergarten, I feel that their level is quite high, they need to do both Chinese (e.g. 閃電, 雷聲) and English dictation (e.g. typhoon, flood) every Monday, so I don't push him too much and just do simple revision on Sat.