How so? Let's consider an example of two students who grow up in the same community. "Steve" leaves school at 15 because he is not engaged in learning, perhaps because he is told (literally or through the actions of his teachers) that he doesn't have the same capacity as some of his classmates. Steve's early departure likely limits his career options and earning opportunities. Meanwhile, "Karen" is encouraged by her school experience and eventually enters a post-secondary program in which she studies science. A few years later she completes the program and begins work for a large pharmaceutical as a research scientist. Although a simple example, and with very limited consideration for lots of variables, it does illustrate how education can help, or hinder, a person's access to economic means.
On a deeper level, schooling is also a place where children and young people learn the various norms of society. It can be a "place" that reinforces cultural expectations. This is not necessarily a bad thing! For example, teachers can model fair and just assessment of student work. This is a cultural expectation we have: All things being equal, if I complete my work in a satisfactory way, I will be appropriately rewarded. However, schools can also perpetuate stereotypes that are outdated and/or unjust. For example, a children's book that only has images of people who are white in positions of authority is perpetuating a cultural stereotype that those who are Caucasian have an inherent right to positions of privilege.
Paulo Freire said it well: