FruityDragons: we will ask the school about supervision. One teacher told me that DD can't stay in the classroom when others go to the instruction class exactly because of the supervision issue. DD is quite self sufficient, but I don't know what the school needs/is required to do.

Mana: DS actually thought about viola for exactly this reason, but he didn't go for it, because it would take him a couple of days to read alto clef fluently, then there is the rest of the school year. :-)