School is a social experience as well. Children get along best with children of their own age, and sticking precocious six-year-olds and dumb-as-dishwater thirteen-year-olds in the same classroom is just asking for trouble.
We should arrange by age and then by ability. Split each year into three streams: 10% "smart", 70% "normal" and 20% "dumb". The smart kids get whatever they need. The normal kids get a good solid education. The dumb kids get ponderously taught the basics of life, to make sure they can read, do basic mathematics, and avoid vastly stupid life decisions.
We should arrange by age and then by ability. Split each year into three streams: 10% "smart", 70% "normal" and 20% "dumb". The smart kids get whatever they need. The normal kids get a good solid education. The dumb kids get ponderously taught the basics of life, to make sure they can read, do basic mathematics, and avoid vastly stupid life decisions.