Furthermore, it says right on the site that versions 7 and previous are affected. Why is it that your school admins/IT dept haven’t deployed version 7/8/ or 9 if they are vista/Windows 7?
Don’t think Avast should block it though, it’s a browser vulnerability, not a virus. Avast is an anti-virus program.
If it’s not a virus, Avast shouldn’t have anything to do with it.
If it causes a problem, your IT dept could prevent you from visiting the site in about 5 seconds by using the FREE http://www.opendns.com or by upgrading to newer software.