in fact Apple promotes that you can drop music from iTunes into an iMovie then post it to dotMac via iWeb FOR EVERYONE TO SEE AND HEAR.
In fact, Apple doesn't promote posting of commercial, copyrighted music to public web sites at all. The Terms and Conditions of .Mac explicitly prohibit material in infringement of copyright.
Sharing music between teachers, except where such sharing is for educational purposes and so falls within the "fair use" allowed within US copyright law, is just as illegal as if you shared with your friends. And download stores carry, by demand of the content owners, even stricter restrictions on use than do CDs, so by terms of use of the Store, even such usage may be disallowed. Consulting an attorney is, as I stated in my first post, highly advisable.
are you saying that everyone who holds a party and plays their purchased music is breaking the law?
They could be, yes, if the party is in any sort of public venue. And yes, the record companies do police such things and have been known to start legal action in such instances, though it's much more likely to happen in cases where a professional DJ has been hired.
just do it because what idiot is going to sue a school?
The RIAA would, and has. Trust me, I work for a school; they will quite readily go after schools for copyright infringement.