Does anyone know on what numbers the skills of the u-21 players are based?

Is it on the level of the U-21 development site or is it based on the level of the manager?
Apart from taking fewer days I don't see much use in trying hard to upkeep your academy at lower levels. I'm level 4 but my academy is the Mini camp I guess, which lists as level 5 so will I be getting better youngsters or just the same as last time?