If your school blocks you, you will end up with problems from them getting around it. Your best bet is to find out what firewalls they have in place and look up ways to get around that, instead of asking how to get HnH to work.
While I do agree that playing in school is stupid, is that the place of people on the forum to tell him what he 'should' or shouldn't do with his time? I've had classes where in freetime you could do as you please including playing any game as long as you can get it to work, teacher's condoned it so what's wrong with it?

If you live in America:
Don't do anything stupid, watch any file anyone gives you, in America at least it's taken very very seriously if you hack to get past the firewall and they catch you, me and a friend put a trojan on the network before, I didn't get caught because I was smart enough to back away when it was happening, but the FBI came and locked up my friend for a day. Someone telling you that 'this will get through it' could be helping, or they could be severely hurting. Cybercrime tends to go on permanent records by the way, so if you don't know what your future holds for you getting caught for such a trivial thing even if it wasn't intended can make it so that you never get certain jobs in the government.
There are typically ways to get around the basic stuff however by obtaining teacher passwords (one of the easiest ways) connecting to the network through a computer that isn't firewalled, logging in through alternative means that don't require an account (if they still run XP this is the easiest way), and several others, google around and you might find some websites for it.
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