Edit: [2] expands the measures to include educational attainment and family outcomes. Reference [3] relates to socio-economic class, while [1] relates to race/ethnicity. [2] was the one I had in mind during my original comment.
[1] Krueger, A., 2012. Estimating the Effects of College Characteristics over the Career Using Administrative Earnings Data Stacy Dale Mathematica Policy Research.
[2] Ge, S., Isaac, E. and Miller, A., 2022. Elite schools and opting in: Effects of college selectivity on career and family outcomes. Journal of Labor Economics, 40(S1), pp.S383-S427.
[3] Dale, S.B. and Krueger, A.B., 2002. Estimating the payoff to attending a more selective college: An application of selection on observables and unobservables. The Quarterly Journal of Economics, 117(4), pp.1491-1527.
I'd be curious about how success is defined here. Career is a pretty narrow lens to define it by so I'd hope for something more expansive.
Many of the benefits of having friends in high places are outside of traditional career ladder. The expedited (insert annoying process here), the vacation you're invited on, the unintentional influence you have on some big thing because you happen to be an ear to the decider, etc etc.