I have been to several shows at the school where my S17 is pursuing a tech degree and i have observed that the performers run the gamut in size and looks, though all are talented. Perhaps you can look at photos of the classes or the shows at various schools and get an idea of what the physical body types of the members are. This might be more telling than just asking because I bet that few schools are going to tell you that they body shame students or don’t accept kids who don’t meet physical norms.