How to prevent the average user from inserting bad code?

I installed wordpress as a backend for our university website and pretty much every semester someone new is updating the site. What this means is that, invariably, someone copies and pastes code which breaks the site. For instance, someone might insert some text which has <div> tags in it, and then put a <!--More..> tag in the middle, thus breaking the CSS for the whole site.

I know there are ways to properly cut and paste text copied from MS Word without creating such bad code, but it seems difficult to be sure people do things properly with such high turnover in our office. Is there a simpler way I can ensure that posts aren’t breaking the site? Is there some way I can automatically strip <div> tags or post an error message if someone tries to post bad code?

Thanks for your help!