@stanger I believe UC’s, especially UCB, use a lot of data to track how enrolled students perform. This includes the CA high schools and the UC’s are aware of which high schools have low API rankings. Generally, graduates of high schools such as Lowell, with a high API index, perform well at UCB, other UC’s and other colleges. Students who attend these high API index schools have a higher chance to do well in college.
Myself being a graduate of Lowell and very familiar with the school, I use Lowell (using i.e., SAT scores, etc.) as a benchmark to compare it with other high schools in the Bay Area, including my district high school. To my surprise, if you are looking at National Merit Winners, there are a few public high schools in the Bay Area that exceeded Lowell’s numbers in NMW. I recall, even some low API performing schools, such as Mission, has a NMW. The point is whether a student is from a low or high API index school, the student can still get into any college if that student meets all the criteria looked at by the admission officer. However, high API high schools tend to give the students a better chance to succeed in college.