this is a classic confounder problem. I'm assuming the vast majority of parents who can afford 40k annual for their kids are relatively well off, have a lot of other disposable income, and the kid is never really lacking for any needs. put them in a public school and it's likely they'll turn out equally ahead for their grade

socioeconomic status (SES) is very often a huge confounder when it comes to anything from health issues, educational outcomes, and many other things. rich kids do better - the SES of the parents of Nobel Prize winners [0], young athletes [1], etc are all indicators of this

[0] https://www.chemistryworld.com/news/nobel-prize-winners-far-...

[1] https://www.sciencedirect.com/science/article/abs/pii/S14668...