Since elementary school (Currently in HS), the schools have provided us with Macs. We had Power Macintosh G3s, iBook G4s, and eMacs in elementary school (which we're getting replaced with iMacs G5s as I left) and middle school had eMacs and iBook G4s but my HS has 2007 iMacs + MacBooks (probably because my HS is fairly new). Either way, they've been teaching us on a Mac.
You are lucky. My schools were all PC based, excluding 4 Macs for "Media" and a few iMacs for Music. (The Media Macs were PowerMac G4 Dual QuickSilvers, with a Single Quad Mac Pro in the editing suites - I used to do all my editing on my MacBook - its a lot faster..).)