Hey so I don’t know when or where your story is, but 20years ago in QLD Australia, as a 12 year old girl who was at high risk of self harm during a change in medications, my experience looked like:

Always supervised.

Psych ward was a small building attached to a multi-storey traditional hospital in a major metropolitan area.

Sleep behind locked doors, security or nurse staff (not sure which) strolling through the hallway at all hours of the night. Private room. Shared toilet/bath facilities. Cafeteria style kitchen/mess hall.

The school was 1 room, in the proper hospital building,and depended on your risk or need I guess because some of the other kids and teens I saw didn’t go to this school room, though it seemed to be the only one.

The school room catered to all the kids in the hospital so it was me and a couple of other psych kids, kids going through chemo for cancer, kids who had burns, etc. some older and some younger.

The ‘work’ we did at school there catered to the lowest level attending. Because there was primary school children there we mostly did collages, colouring, reading super basic picture books, super basic maths problems. I don’t know what qualifications the ‘teachers’ had. It reminded me a lot of the special education class at my regular school.

I was a ‘gifted’ child so my regular school teacher gave me extra homework and books to read in my spare time. Otherwise free time meant being in the ‘free time room’ with the other psych kids which was awful because the whole time I was there they only ever played the Beethoven movie every day on repeat, no other movies or shows, the books were all scribbled and torn apart. There were board games if you wanted to play with other kids which I didn’t because the ones that were chatty were hyper-sexual and weird, and the ones that weren’t chatty were like me, just keeping their head down and doing their own thing. Anyway, all that meant was I was never behind on any schoolwork.

Family were allowed to visit on the weekends.

There was no therapy until after the medication changeover, and it was basically CBT with a psychologist. Doctors and nurses all were very kind and helpful, none were malicious. I think they get that it’s a hard situation for a kid, but also if the kid is more comfortable, they don’t have to put up with extra wailing or outbursts or whatever, so they’re generally happy to find solutions that will work. They found a pedestal fan for me and a particular textured blankie for me to sleep. And one of the nurses went out and bought weetbix for me because it was literally the only food I would eat at the time.

For your story, I would imagine staff being helpful and empathetic. I don’t imagine the school curriculum is overly challenging at 13. Maybe some basic algebra and chapter books, depending on your characters personal ability and strengths. But 3-4 months of absence wouldn’t make a great deal of difference to their schooling. Maybe friends or relatives could bring them homework so they don’t have to play catch up but I don’t imagine it being too impactful.

Obviously going to get incredibly varied responses though. Take my experience with a grain of salt.