I am not sure that overrated is correct. I believe that the main point of school is teaching you how to think.
Having been around people and worked with people with very little education, there is a bit of "how to think" that is missing.
Some of these people are quite smart, but I believe that there is a limit to what they can do due to the lack of education - I think that because they only went to school for a short time, they are "lack" how to think and approach problems.
Of course there are always exceptions, and there are certain jobs that they can do, and can do them very well. But there limit is much lower than someone who has finished school.
And really, isn't training another word for education?