I've only used the version of BS in that thread, so I don't know about the later versions.

If I go Setup > Options > Connection, I can see the listening port. Mine's 6348, I think that's the default port.

If anybody else at school can use LW or FW, ask them how they've set things up. If the port test doesn't work, it means that something's blocking LW's default port...and so probably blocking FW as well.

You really should check with the school...if you get caught using p2p when it's not allowed, you could be in deep poo.