In her class, she was 39th out of 559. She was in the 93rd percentile of the only group she could compare herself to. Prior to college, I would say she was a phenomenal student compared to her peers.
The point of the article is that low-income kids, despite being intelligent and doing well among their peers, have a hard time transitioning to college. Universities could wash their hands of the problem and just reject the poor kids and send them to two-year universities like you suggest, but they’re trying to solve the inequality without further exacerbating our income differences.