For SAV for Mac:
Symantec AntiVirus for Macintosh Auto-Protect error Code 6 (or error Code 10) on startup
http://www.symantec.com/docs/TECH103860
It needs to be version 10.2.3, which is the Snow Leopard supported build. If the operating system is running in 64-bit kernel mode, this is expected, as 64-bit kernel mode is not supported with SAV for Mac.
Upgrading the operating system without removing SAV first may also contribute to this issue.
You can use this utility to remove SAV, but you will need to speak to your school about getting a new install package. Frankly I recommend Endpoint Protection (SEP) for Mac version 11.0.6300. It is fully compatible with Snow Leopard in 32-bit or 64-bit kernel mode.
Removing Symantec programs for Macintosh by using the RemoveSymantecMacFiles removal utility
http://www.symantec.com/docs/TECH103489
Good luck,
sandra