Realistically, “guesstimates” are all that you can get. I doubt that any college (except maybe religious schools) requires students to explicitly reveal their religious orientation. So they don’t have hard data.
Even if a college did ask students to reveal their religious orientation, the results might not be straightforward to interpret. Maybe there are halachically Jewish students who have decided that they are atheists and no longer identify as “Jewish”. Or maybe there are students from totally secular, non-practicing families who nonetheless do identify as “Jewish”.