ports can be changed in Trillian, or a port forwarding utility. another problem we have is there is an a level programming course, and they write in C (and some in assembler), C Sharp, and .NET.
pain when you look through the names.
we use a service that blocks pretty much anything on any port (unless we need it, and ask them), however another school i know, uses thier own ISA server to block everything. Brilliant.