What you asked won't help what you want.
For the IRCds I specialize in, they set certain port ranges for mIRC. Whereas on a java applet (which can use different port ranges), they haven't been blocked and therefore, you can bypass it.
On an Unreal IRCd network, though, I have found that both mIRC and java applet users connect to the same port. So in that case, going through a java applet won't work.
But if your school will actually support a port that mIRC can connect to, then /server network:port.
Use the colon to separate the name of the network and the port.
