I left school with qualifications way lower than I should have (mostly GCSE C grades), although I was in the top set at everything, and should have really got A's and went into further education, but I didn't I hated school.
Since then, I've gone from fairly meanial manual jobs, to a quite technical manual job, to a quite technical engineering job, to a very technical CAD job, to a technical architectural job, all without "external" training.
Sure, my wage isn't high (£32K) , but I got there on my own, to be perfectly honest, I really don't think there is anything that anyone can teach you, that you can't learn yourself.