If training young footballers seriously, we would never suggest that they continue to play past primary school age with players of all abilities. It OBVIOUSLY would mean that either worse players would not get to play competitively and best players would not be stretched.
Why don't we take a similar approach to education?? One of my issues with the U.K. education system is it rarely holds children back even one year despite them not passing basic requirements for a year and it is not commonplace to move children ahead one year.
I think there should be the ability to hold children back for max 1 year and move kids forward by max 1 year so that classes are more indicative of ability, and streaming of abilities across all subjects year to year (to allow movement between years).
Everything feels like it is amount the lowest common denominator (particularly in state schools!) which holds back brighter children imo.
This would be much better than having a separate grammar system which separates kids out so young and does not allow for late bloomers