For me, what lacks a lot in (high school) stories is FRIENDSHIP DEVELOPMENT. Most of the time, they have a BFF and everything is always super-duper, never had a fight and always agree (for me that’s unrealistic). But back to high school stories, it would be nice to see the link between MC and her friends, because high school is all about friends imo.
I don’t mind reading a high school story (even with some cliché), but it has to be somewhat original.
Like I said above, development . Maybe some fights (not necessarily), but things that were thrown in their way, but that they overcome at the end (idk if you get what I’m saying lol)
For me, it’s all about the dialogue, sentences can tell a lot.
Ask yourself if the scene is important to the story. If it’s not cut it out. When I say important, it doesn’t necessarily mean that it has to be a big scene, but for example, ask yourself “what is the reader going to learn from this scene?” if there is no answer, then maybe the scene is not useful.
I would say, let her express herself in her own way and “don’t be afraid to make her sound like a robot” because I think that would be the way people would see someone talking with words they have never heard lol. But make it look natural I would say
Hope this helps