Going to school or college is much more than just passing the tests. The human interaction, the relationships you form, the ideas you will be exposed to, the things you will learn to avoid... There's value in the education process that goes well beyond the final certificate.
Yes, you can always think up some way to get the same benefit, but the point is that for most people, going to college is a good way to get a well-rounded education that involves being exposed to a range of ideas and people. Can a dedicated person figure out a cheaper alternative? Possibly, but that's beside the point.
