Sports are extra curricular activities. And recommendations are a way for a struggling student to get a second chance after grades and test scores. The privelidged would presumably have those covered either way thanks to tutors and a stable household or whatever.

However when it comes to selective schools in particular, if gifted poor and lower middle class students are being edged out by wealthy kids with average-to-above-average abilities, thanks to parental connections and "working the system", then I totally agree with you there.

Though I don't know that your list of advantages are things I think of as "middle class".