If you need to just get some generic "good job", then the answer is to learn what you need in the first twelve years of school. I think that's enough time."
Some guy on the internet said 12 years is enough to get a good job so I guess its true? A number other than 12, the product of history and chance, must be a sinister plan to uh extend childhood indefinitely by some cabal for some mysterious reason.
(Full disclosure, I went to school till I was 28. It fucking ruled and I think everyone should do it if they want to).