If public schools weren't institutions which arise from and abet coercion, maybe these things wouldn't happen.
The primary question shouldn't be why did the cop attack a girl?
The primary question should be, "if public schools are so good, why do they require force to fund them and why are the cop / thugs there in the first place ? " The present system simply verifies that a forcibly funded indoctrination is the goal, not a real education.
Real service providers DON'T USE GUNS TO capture their customers!