www.asd.edu.qa is the American School Doha - it has an excellent reputation with fees and waiting lists to match -

There is a Canadian School (which follows the Alberta curriculum) but their reputation is so-so and only goes to grade 9. They are affiliated with the College of the North Atlantic Qatar.

Any of the better schools have waiting lists - start contacting them now.

School year will start at the end of Eid (probably around the second week of September depending on the curriculum followed (British, US or Canadian)