I was at boarding school late 80's to mid 90's. I agree with op's it is what does not happen at school.
Before I went I thought it was going to be all Mallory Towers, a massive sleep over with friends and midnight feasts. The reality was somewhat different.
The lack of privacy and having your own space is horrible from a teen girl. Yes, I used to walk 'home' from school to my house, but instead of being able to go to my own room and unwind - I went to my dorm, which I shared with 7 other girls and was never quiet.
you are at school 24/7 and there isn't any respite from it. You learn to shut down your emotions, which is not healthy for pre-teens/teens.
You train your self to survive it because no adult really cares for you. Unwell, have a bad period, feel homesick or want a cuddle? You soon learn that you are on your own and know no one is coming to help you and that you cannot show upset, or worse cry because ( that is wrongly) perceived as weakness.
The friendship fall outs and drama that went on was intense .
Being an all girls school lots of girls got crushes on other( usually older) girls. (at a time when same sex relationships were seen in society as taboo) this caused a lot of anguish and allowed for a system of abuse of power and bullying . Usually the girl with a crush would become the dogsbody for the girl she had a crush on.
Lying to parents about how much you loved school when you were miserable.
Boarding schools may have changed since my time, I hope they have, but it is still an emotional trauma for the child.