You're right to be hesitant to choose a school that doesn't have a dedicated gifted stream or an ability to personalize learning to the individual student on a subject-by-subject basis.
Personally, I've opted for a small Montessori-flavoured private school for my DS6 that allows a great degree of individualization by subject. The small class size and flexibility of the staff in meeting my DS' needs as an individual learner have been paramount in his happiness and achievement of a good academic fit. At young ages, my personal opinion is that administrator and teacher openness and flexibility to individualization trump a school's overall reputation in terms of fit.
ETA: I should add this--achieving a good academic fit goes a long way to supporting social and emotional success. It can be stressful for a young child to experience friction between his/her needs and the classroom offering if there's a wide disparity. Alleviating that stress and providing an appropriate level of challenge can be a successful springboard to helping a child open up and thrive on the social front.
Good luck, and welcome to the forum!
