Giving this school the benefit of the doubt by assuming they're not insane, chances are that they got a sweet bulk deal on some surplus stock - someone went bankrupt or had a large order cancelled.
Sure you can. All but the very first Intel macs have included a "BIOS emulator" in their firmware, so they can boot from PC-format CDs and hard drives.
This is factually incorrect.
You cannot boot a 2011 Mac Mini with a Windows install CD, nor a linux install CD for that matter (unless the latter has been built specifically for EFI mode booting).
I have not tried it but Windows 8 *might* load since i believe it has EFI support whereas Windows 7 and earlier does not.
But anything needing a bios will not boot on 2011 Mac Minis. I would guess the same is true of 2012 minis too, since they are essentially the same.