Angela Brazil, Dorita Fairlie Bruce, Antonia Forest for girls and Frank Richards (of Billy Bunter fame), P G Wodehouse and Horace Vachell for boys.
I read many of these, as did my dd2, who loved that era books. Her favourite were Gwendoline Courtney though. She loved the gentle nature of them. "No wrecks and nobody drowning" really.
When I read them, it was as a bit of a lonely girl imagining in a parallel universe being there with lots of friends.
We both loved the Chalet School. In fact dd2 was very disappointed to find we couldn't put her name down for it. She had a brown and flame uniform (including gym slip) she used to walk round in for a while.
All of me dd1 and dd2 read Malory Towers and St Clare's. Preferred Malory Towers and found the continuations rather cringy though.
I liked Trebizon series (the author was one of the people who wrote the continuations for EB, I think) but found them a little too edgy at times. They felt so grown up with their older boyfriends etc. Neither dd1 nor dd2 enjoyed them at all.
DS found Stalky and Co fascinating. He loved the off the wall-ness of them. He called people "Popularity Prout" if they annoyed him for a while. He thought some of the infernal trio's antics were hilarious.
I've only read a couple of Angela Brazil and found them a little too dated even for me. Dd2 I think they were the ones where she found the too much Morris dancing boring.
Loved the Dimsie books, as did dd2. She's a interesting character - totally captivating in a book, but I suspect would have been incredibly irritating in real life!
Antonia Forest, great books, very different to the others in that the children are not "for the honour of the school". I preferred her non-school ones, especially the historical pair, but I think that's partially because I prefer adventure type. Dd2 loved the school ones except "The Attic Term" that she found too sad.
Ds loved the historical ones though.
Frank Richards. I've got one Bessy Bunter and read some of the Billy Bunters. Tbh I just ended up feeling sorry for Bessie/Billy as they were so unaware of how they were seen by the others, which spoilt any enjoyment. I suspect we'd diagnose them with ASD nowadays.
I don't think I've read any school stories by the other two.