Why would it have to be a one-time selection? Put kids in a class based on their current level of academic performance. If you're doing better than the other kids in your class then you go to the more advanced class.
It's possible the reason for that is that the original assessment was well-calibrated. But if you want to see more opportunities for misidentified students to prove their worth then why not argue for that instead of making every class the dumb class?
It's a somewhat self fulfilling prophecy though, isn't it? The point of splitting kids out is that it will push them forward academically; by being held back because of their performance at one point, it makes it that much harder to excel further down the line to jump in to an accelerated class.
Why not take the top 20% (or whatever number) of the lower class, and give them a change to go to a higher class? and the same for the bottom 20% of the higher (who maybe aren't able to keep up) to go to the lower class.
