In order for a dental school in the U.S. to be accreditade, which it has to be in order for its graduates to take a liscensing exam, they HAVE to teach composite fillings, so their isn't a dental school out there that doesn't.
As for mercury safety, ANY properly ventilated area is sufficient, since the vast majority of mercury used is in the bound, inert phase. The problem with the mercury topic is that alot of anecdotal, non research based, notions are sold to the mainstream media who runs with the idea. Claims of removal of amalgam fillings curing one's medical conditons cannot be proven scientifically. Additionally any claims of amalgam causing disease cannot be backed up scientifically, and dental amalgam is one of the most researched materials out there.
The way that I explain dental amalgam/mercury to my patients is a simple comparison with table salt, NaCl. If you take elemental sodium by itself, its highly flammable and dangerous, if you take elemental chlorine by itself, the gas will kill you. Combine them and you have perfectly safe table salt. Similiar with mercury, in its elemental form, its toxic, combine it with the components of amalgam and its an inert, safe element.
Scientifically backed research is a powerful tool, thats why in the last few weeks, 2 pending laws reguarding amalgam have been throne out due to lack of research behind the claims.