I'm not primary, but even when you start in January, classes are set, so it won't be your class. I would do everything the way that the children do it now unless you really feel very strongly about doing sonething differently. That way, you'll feel in control because the class will co-operate collectively out of habit. If you try too much retraining, they'll be unsettled, and youre setting yourself up to be judged unfavourably against 'their' teacher, so consider how much you'll gain. After all, you'll only be covering that group for a term, or a little longer and it sounds as if you are getting an established class, not one that has had a lot of supply teachers.. Presumably, you'll get a new class in September if you're still covering, and that's the time to establish yourself as their teacher.