Usually on school campus you'll have wifi too, and also 802.1X protection is there for a reason.
The only way to share internet from a 802.1X protected network , I think, is by creating a VPN connection on the mac (this will only work if your school's network allows it which i doubt).
To do this go to your nettwork settings, unlock it (padlock) and click the plus sign to add a VPN connection.
Next you choose VPN connection, in this example i'll be using vpnbook.com/freevpn since it provides a free reliable service. So change the type to PPTP.
Now the interface is created and you need to put the credentials provided in the free PPTP section of vpnbook.com/freevpn (vpn server / login / password)
hit connect and it should work
The last thing now is to share this VPN connection, you need to go back to share settings and choose the interface you just created
I can't post more than two links(images) since this is a new profile, if you need more help comment.