This was the idea behind California's Master Plan for higher education, instituted some 70 years ago now: anyone is eligible to go to a community college for two years, and if they do well, they are guaranteed entrance to the California State colleges or to the prestigious University of California system (depending on performance).

It works well. If you look at graduating GPA from UC Berkeley and UCLA, you find that the stronger the candidate was going in (higher SAT, HS GPA, etc.), the higher the average GPA coming out, the lower the dropout rate, etc.. No surprise there.

But then you look at transfers from community college--who initially were nowhere near making the cutoff for UCB or UCLA, and if they had been admitted would have been the weakest candidates there--and you find that they are every bit the equal of their peers who had entered with good grades and test scores.

Now, there's a question as to whether this is enough. But it has been working well in California, and has been widely studied and sometimes emulated by other states and other countries. California has, in recent decades, been kind of dropping the ball by under-funding the system and weakening the guarantees, precisely when (due to Prop 209 ending affirmative action for university admission in California 25 years ago) it needed to be strengthened.

It still is powerful documentation: this works.