Five classes a day of rote memorization and creativity-building exercises is a bad proxy for ability.
Schools are designed to pick the best, a combination of talent/intelligence/motivation, and slot the rest in places where they fit as workers. (We are all free; we are all workers, comrades!)
Instead what they end up doing is boring the good students, seeming irrelevant to the rest and picking only obedient fanatics to succeed. This explains why our leadership is so bad; we're promoting the wrong people.
A better way might be to stop spending so much time on repetitive activity and let students work on a project-based method, much as they'll do in their future jobs.
But that ruins the real purpose of public schooling, which is day care so both Mommy and Daddy can plug away for maximum income.