I'm certain there'll be hidden costs. And hidden (to some) benefits for Open Source

It seems obvious that there is a big advantage to schools in using software that students can install at home and use there. If, for example, students were using Inkscape to create graphics. They could take their work home, use Inkscape at at home. I realize that not every kid has a computer at home that they can install software on, but with something like Inkscape which runs accross many platforms (Linux, Mac, Windows plus other user supplied ports {an additional value for schools - which strive to be inclusive}) this has to be a benefit.

This is just one example of a program that does a great job in a area that usually requires expensive software (and IMHO has a great interface for people learning illustration) . There are a number of other examples, desktop publishing, music, and for younger kids Sugar and all the activities from the OLPC project.