This is a good question. Here are a few points to get you started.
First, socio-economic status make a huge difference in achievement. This point should be clear. Money and social status can buy a child a lot of advantages such as private schools, tutors, and so many other after school programs.
Second, with wealth a person feels more confident and comfortable in places of power. This social dynamic, which cannot be quantified also plays a huge role in getting ahead. Pierre Bourdieu has done excellent work in this area to show this point. He calls this social capital. In short, knowing and experiencing what society deems useful and good enables a person to get ahead. Social status and wealth gives a person a huge head start in this area.