Our DD has had lessons with BASS in Morzine and LGS and I can highly recommend either ski school. LGS is a smaller outfit than BASS and Tim Scott, who runs it, is an excellent instructor. You might find that it's down to what is available outside of school holidays as they have to get appropriate numbers of children of the same level to be able to form a group. We were in Les Gets one March and BASS couldn't accommodate DD at the level she was on but LGS could. I would give them a call soon and see what is available.
DS1 went with 360 in Les Gets in 2012 and we were really happy with them. He was a beginner, but he made good progress and enjoyed the lessons. He was four at the time and messed about a fair bit, but the teachers were very nice about it (we spied on him one day and he was being a bit of a pain, but they never said a word!)
We've just booked to go to Les Gets at the end of February as part of a large group. Does anyone have any reviews of ski schools there, good or bad? I'm looking at BASS (mega expensive!), LGS and Ecole de Ski 360. We have some older kids who have skiied before, some older beginners and 4 little ones who will be 4/5.