The router already separates your little private LAN from the school LAN. The router runs something like 192.168.1.xxx for your internal LAN. NAT (Network Address Translation) hides that private network from the network on the outside of the router (your schools LAN). Just ensure that your wireless is locked down...disabled if you don't use wireless, or if you do..use WPA2 security. Ensure your routers web admin password is good.