It's been a while since I was a student, but assuming that schools' attitude towards technology is still the same you'd probably get detention and your school-issued Chromebook confiscated if you tried to enable developer mode.
The vast, vast majority of kids don't know it exists and have no idea what they'd do with it even if it did.
Yeah, I'm sure there's the one kid who loves tech in the class that wants to use it, but they'd be just as interested in Linux/tech stuff whether or not the school handed them a Chromebook.