My colleague, Chris Dawson, has written several excellent pieces recently about Linux (mostly about the latest from the Ubuntu family of products but more recently about SuSE) and he has made some excellent points. The question one has to ask though in deciding whether Linux is right for your school is this:
Does your school's IT department have the expertise to support a robust Linux thin-client model with Linux serving both generic personal productivity applications and Windows or Macintosh-based discipline-specific instructional applications? How about a simpler standalone Linux environment?
Yes, we can look at the success Chris has had and say "See?" but how many school districts in the United States have someone on staff with Chris' level of expertise? (The fact that I have to qualify that ought to concern us all.)
Chris has a 10/100 base-T network at home serving applications to his kids via thin clients for goodness sake. And he is spending his summer doing some heavy-duty experimenting with Linux so he can provide even better service to his faculty and students come fall. Let's not forget either that Chris worked in IT in the private sector before moving into education IT.
Remember too that at school Chris operates a mixed environment where his Linux thin-clients serve his students personal productivity needs but his faculty also rely on Windows and Macintosh in order to meet their particular instructional needs.
On the university level, the answer to the question regarding sufficient IT expertise on staff is almost certainly yes but on the primary or secondary level, that may not be the case.
Even in a university, where Linux has a significant and growing following among researchers, the overwhelming demand for instructional computing is still in a Windows setting. Even demand for Macintosh services tends to be discipline-specific (music, multimedia, and fine arts.) At my university, even computer science relies as heavily on Windows (and Windows ports of their favorite open-source software) as they do on Linux for instruction.
When assessing your schools IT needs, it is critically important to keep in mind that the depth of your school's collective IT expertise plays a big role in your ability to support one technology over another.