Mayer's study was based primarily on low-income families, but her results apply even more powerfully to middle- and high-income families. If money doesn't make a big difference in the lives of poor children, its impact is even smaller for kids who are already well provided for.
Mayer found that the things that make a difference are relatively inexpensive: the number of books a kid has or how often his family goes to museums. She argues that all the other stuff — summer camps, tutors, trips to Paris — are like upgrades on a Lexus. They're nice to have but immaterial when it comes to getting from one place to another.
George Mason University economist Bryan Douglas Caplan takes an even more extreme view. In his provocative 2011 book, "Selfish Reasons to Have More Kids: Why Being a Great Parent Is Less Work and More Fun Than You Think," he cites studies of identical twins to argue that once a child's genes are in place, there's little that parents can do to shape how their kids turn out.
If private tutors or the right address is unlikely to change a child's life, the relationships kids have with their parents just might. This is the argument that University of Pennsylvania professor Annette Lareau advances in her groundbreaking ethnography "Unequal Childhoods: Class, Race, and Family Life."
In the mid-1990s, Lareau began one of the most in-depth observations of American parenting ever conducted. She spent a month each with 12 families (six middle- and upper-middle-class and six poor or working-class) and observed how these parents interacted with their children. Lareau concluded that middle-class parents convey substantial advantages to their children in three ways: by cultivating their interests, enriching their thinking and speaking skills through informal conversations, and teaching them how to navigate institutions such as colleges and workplaces that serve as de facto gatekeepers for success in America. Success in those areas is much more related to the amount of time parents spend with their children than where they send them to school.