One thing to keep in mind with a lot of educational software (software targeting schools more so than software targeting parents at home) is that a good portion of the computers have minimal 3D capabilities. A lot are also running with minimal RAM as well. One of the reasons that Macs are so popular with the schools is that they get new Macs from the various bailouts by the Fed (can't have Apple go under, otherwise Windows will have a very real monopoly...so every few years the government spends a few hundred million dollars on new Apple computers). However when it comes to PCs a lot of them are second hand from other government agencies (DoD, IRS...), so by the time the schools get them the hardware is already 4 or 5 years old. Point being, the best bet for most broad reaching educational software is no 3D or a very efficient software renderer.

A project I did a couple years back for a study group in Texas came acrossed that problem. Their original contractor had problems and one of them was meeting hardware requirements. We ended up using plain old flash animation and actionscript. We were able to run on almost any computer, and the actionscript allowed us to connect through the network to a central PC. The main executable was Windows only, but since the flash clients did not need to be a specific OS - the schools only needed one Windows box for each cluster. Also, with a bit of help from a handful of flash experts - we were able to effectively simulate 3D movement and interaction, collision detection and even some simple physics behavior...all using the action script (which is really quite simple).

Anywho - depending on what you are looking to create support for Mac might be nice...or you might loose a contract altogether. However having a 3D accelerated engine that will run on Macs may not help much if the Windows PCs can't run them to begin with. I think that would be a better path in the long run to pursue as opposed to support for Mac...support for piss poor old hardware. Lack of either might cause you to loose a contract.