Whatever your views or prejudices regarding flap selection when wings are not level, it is still worth teaching students to be able to select flap while turning. It can help keep the circuit tight (yes, that old chestnut) and may even be essential at some fields. If you are doing a military type circuit (ovals not squares) it may be a local requirement to take flap while turning base.
May as well teach the students to be competent at it, even if it is not something you would do yourself.
I