Maybe colleges can just accept the best students and do their job of educating them instead of arrogantly appointing themselves as saviors and righters of all wrongs in the world.
Higher education is the most potent tool for breaking the cycle of poverty. Your plan would lock people into the cycle of poverty for generations.
Besides, how do you even define "best student". One that scores the highest on the SATs and has the highest high school grade? There's so much more to being a good learner than having the opportunity to get high grades and high test scores.
In the USA, at least, "every student college bound" has led to colleges being simply more high school but at an enormous cost of creating indentured servents.
It will be very hard to to force colleges to downsize to the appropriate population count. Lots of prestige and money on the line
Besides, how do you even define "best student". One that scores the highest on the SATs and has the highest high school grade? There's so much more to being a good learner than having the opportunity to get high grades and high test scores.