This is not an ethical hacking question. The school is 100% within its rights to determine what its internet connection should be used for, just as you are if you pay for your own private connection (you wouldn't necessarily want your neighbours downloading kiddie porn for example, and neither would you be impressed if your neighbour posted to a forum something like "my neighbour cpulocksmith is such an asshole, he won't let me use his internet connection for free to do illegal stuff").

If that upsets you then that's just tough doo-doos. Get over it.

The day kick-off is probably a warning; check your school's policy. Repeated violations and attempts to get around the kick-off may result in your internet access being revoked completely and possibly further disciplinary actions taken.