I have always taught (and been taught) to limit the angle of bank in a climbing turn to 15° and to try to avoid extending the flaps in the turn, but sometimes it can't be helped, for example during a glide approach. Cessnas have a large nose up pitch change when flaps are extended which could get a low time student into trouble if they are not paying attention. I make sure turning in the base leg configuration is practised plenty of times at altitude before bringing the student into the circuit. I too am a believer in explaining the situation rather than saying "don't do that because it's dangerous".