This is really late to be trying to find a place for September, try and get his name into as many schools as you're interested in ASAP - There is the ASD, DESS and Doha College which are all probably considered to be the best - but because they are good - their waiting lists can be long.  Some have recommended Compass or Sherbourne as well.  Do a little googling to see about facilities and contact info - then start communicating with them.