It can get very over the top, but it's down to the parents to say no isn't it? and to limit spending to what they can afford or want to pay.
DD will have her Leavers Ball next year, and we have already discussed how we will be looking on the Next sale rail in the local shopping outlet village, or local charity shops, lots of which sell cheap second hand prom dresses.
I will get my hairdresser to curl her hair, and I will paint her nails myself and that will be it apart from sensible priced bag/shoes. A family friend will provide free transport in whatever shiny vehicle they have at the time.
DD isn't part of any "in crowd" thankfully, so won't have to live up to that and will be able to do her own thing. After that she will be thankful to never see most of them again, due to a lot of them being bitches to her.
It is lovely looking at the photos of this years Y11 though. They turned up in tractors, rolls royce, motorbikes, horse, lorry, and even a batman car.