I'm like 90% sure the vast majority of people who do school RPs had unsatisfactory or otherwise totally shit experiences in school in real life so this is pretty much escapism to live out a fantasy of what they wanted school to be.

Can't speak from experience because I roll my eyes every time I see some variation of "Angsty Teenager Academy- With a Twist!", but I'm pretty sure the majority of those RPs don't capture thr tedium of sitting through 50 minutes of chemistry class and staring at the clock while enduring the high stakes adventure of writing notes without developing a cramp.

Considering they're a dime a dozen for roleplays, and most don't last long before folding, I assume most are made without any direction or plot. With few exceptions, that doesn't lead to a good lifespan for a game. You kind of need more than a basic premise to keep players invested.