I never did year 9 sats either, i go to a private school too
But i did have to do the Key Stage 1 + 2 ones
, they're such a waste of time!
At my school, we have people in the IT room patrolling up and down making sure you don't do anything at all "fun"
, but you can go into the Music Technology Room (where there are computers, keyboards, microphones, headphones etc. plugged in), and do pretty much whatever you want