You don't get to opt out of police wearing body cams when they arrest you. You don't get to opt out of public school teachers wearing body cams when they teach you.
Police work is a strawman argument. I’ll give you another strawman: installing cameras in all the bathrooms would prevent abuse in this bathrooms, wouldn’t it? Except all the unintended terrible consequences this plan is bulletproof.
Moreover, classrooms isn’t where abuse happens, by and large. Private offices, bathrooms, locker rooms, are all much more likely places.