I don't think you will be able to break it up into multiple CD's and have the installer work directly from those CD's. It probably won't know that you split the DVD and that it needs to prompt the user to insert another CD. There is a chance it would be smart enough to do so, since Microsoft distributes CD and DVD versions of their MSDN subscription and they may have made the installer flexible enough to deal with either case.
More likely you will need to have your students copy all the CD's to their hard drive so that the original directory structure of the DVD is restored, and then execute the installer from the hard drive copy.
Perhaps it would be easiest to simply require that each of your students spend $2.50 to get their own DVD evaluation version, or $5.00 for a CD evaluation version, depending on their circumstances:
http://shop.microsoft.com/Referral/Prod ... siteID=140
cfitz