Initiating a legal battle is not for the faint of heart. Few want to tangle with authority, and the kind of people that would implement + enforce such a thing

Initiating a legal battle is not for the faint of heart. Few want to tangle with authority, and the kind of people that would implement + enforce such a thing (e.g. school administrators) are notorious for being petty and inflexible. Moreover, they often have lots of legal backing for their actions (due to "in loco parentis" status) that are hard to pin down. Most parents don't have the resources for such a suit (or defense), and most students probably don't want to risk getting suspended/expelled or sent to a different school for being the one who sticks up for their rights.