RE Point 1. All it takes is one of those other peers' parents to allow them to view pornography and then that kid just becomes the porn-distributor for the school, just like some kids in my day passed around porno mags. In essence, nothing changes for the kids, but every single adult is at best inconvenienced and at worst at risk of government invasion of their privacy. Not worth doing, imo.

RE Point 2. They could just use a whitelist instead of a blacklist/filter. They exist already, after all. Fill it up with sites showing the wholesome version of the world you want your child exposed to and they can only visit those places.