If you encounter switchers in your classroom, they may feel frustrated with muscle memory - that they go to hit CNTRL-Z (or CMD-Z) and find when they went to the other platform (which they of course hate), that they hit the wrong key. And it leaves them upset.
Remap Keys on the mac - for example, switch the cmd + control keys:
KeyRemap4Macbook [From KeyRemap4MacBook]
Controller Mate [From OrderedBytes :: ControllerMate]
Double Command - [From DoubleCommand]
Tesla - [From 親指シフト for Mac OS X]
How to remap keys on the PC
Sharpkeys Sharpkeys
How to on Sharpkeys
Keytweak - http://webpages.charter.net/krumsick