All three of my daughters attended pubic school in Japan through most or all of their elementary years. They all scored in the middle of the pack (between 40th and 60th percentiles) in the Japanese equivalent of our Iowa basic tests. First year back home (in one of the better districts in Pennsylvania), they were suddenly in the high 80th and low 90th percentiles. I kid you not.
I Japan, schools still work like when I was a kid.
A student walks to the front of the class, solves a problem on the board, erases it and then the next student comes to the board and is given a problem.
Every student knows where every other student stands (if he pays attention) and nobody fails in secret. Teachers can assign study partners if needed to help with known weeknesses.
Academic secrecy is the enemy of academic achievement.