I don’t think more than 8-10% of 18 year olds are intelligent enough to benefit from college, so “more than 1/3 being unprepared” is like, DUH.
Before 1960 or so only about 10% of all 18 year olds went on to college. It was just assumed, and I believe subsequent experience has amply prooved, that only this small fraction of young people could be called “college material.”