Does your school make you authenticate when accessing the LAN? If so, just getting a router may not solve the problem. In my school we have to authenticate through Cisco Clean Access so I have a computer (spare pc running Server 2003) with 2 NIC cards, 1 connecting to the wall and I use ICS to share the internet through the other NIC into my router (WRT-54G). From there I can plug my main desktop and anything I want into the router and even broadcast my own wireless.