Back when I was applying for college, the UC system, on paper, accepted the top 1/8 of HS grads, the state college system the top 1/4 and the city/community college system any HS grad. Somewhat foolishly I only applied to UC even though my HS GPA was something like 2.9. But I was good at standardized tests and got in with my SAT scores. My rejection and acceptance letters arrived within a week of each other. Graduated in four years which was pretty standard for the time, but is somewhat exceptional now.
Revelle, UCSD grad here. Started Jan 1974, graduated June 1976. Age 19. BA Molecular Biology, minor Psychology, language proficiency in German (SAT II written plus orals with a German grad student). 18 to 22 units every quarter. Summer quarter was 12 for lack of options.