DESS is a primary school only. Doha College is good, but not at the calibre of a good UK public school. If you want to follow a British curriculum, I would not seriously consider anywhere else here (they are the only two British embassy-backed schools). The American School is also very good, but a different curriculum and teaching style entirely.

If you and your child are willing to endure the separation, then boarding school may be the best option if the decision is being based primarily on academics.