The Obvious Solution (Score 2, Interesting)

The obvious solution is to implement a slashdot-like system with regards to reviews. By default, reviews will be given no clout, and it takes review by peers to validate them before they are even displayed. Thus "THIS TEACHER FUCKING SUCKS" which while possibly true offers no value will not end up being seen unless somebody is browsing at the troll level. That way constructive and critical comments will both be available, but only those that are thought out and respectable; anything below that can be taken as heresay.