I went to a boarding school for several years, a forces one. That said, there were a good number of pupils who had very sad family backgrounds, bereavement, poor treatment, close to going into care etc.
Whilst there were plenty of activities, I found the education standard to not be very good and the Head was cold, harsh and unreasonable. As at any school there were good and bad teachers, but you are stuck with them in a boarding school. When you feel relief to get away from that staff member who hates you in a day school, well you can't as a boarder.
A lot is to do with friendship groups as well. When I first started it was awful, I didn't gel with anyone and it took me to year 2 to make friends. One had accused her step dad of assault and the other had lost her mum, both such sad circumstances.
But in general I hated it. I never really got over my home sickness and as we went home every third weekend, it became a cycle of distress. I lived for the weekends at home.
When I left, I always knew that my mum did not want me home. I was an adopted child and my parents were quite elderly. I was right, she didn't.
Lots of the children are very, very homesick particularly the younger ones. Its not all midnight snacks, more bed wetting hell. You have to get up and carry on as though nothing is the matter and it is a harsh learning curve. Please reconsider. Even if your dd says she wants to go, she is too young to make this sort of decision for herself.