Even if you select for ability along some axis, you still get different interests and learning styles - and personalities.
Learning is basically industrial, uselessly abstracted [1] and commodified, when it could be individualised. A lot of talent is wasted because high school stunts the really bright kids. And given how brutal it is, it seems to damage everyone emotionally.
[1] Virtually none of the math you learn at school really makes any sense unless you're one of the small number of people who go into STEM - which is where you finally discover what it's for. Things are a bit better than they used to be, but basic financial math as a specific competence is far more useful to most of the population than even the most basic algebra and trig.