I can't think of any laws against posting public information on a website (I guess unless that information was for the purpose of harming the person). The fact that person ABC works at school XYZ is public knowledge.
If the posts are in any way defamatory then contact the site admins to get them removed:
http://www.ratemyteachers.ca/info.php?type=RateRules
Otherwise it's a legal battle to have the site's host remove them to shut them down.