As for stuff that should be taught,
Electronics, I did electronics at school but it was a very poor program and I diddnt take a lot from it. Someone I used to work with is now a teacher at a tech school devised to teach real world electronics and troubleshooting skills to kids. I know the guy and imagine his courses would be brilliant.
A lot of our new hires and apprentices just went through the motions in a classroom for a couple years yet it can take them a while to learn how to apply the knowledge in a practical manner.
Likewise I think mechanics. I diddnt grow up fixing cars or working on engines. My first mechanical experience was a basic introduction to aircraft mechanics and I diddnt know wtf half of it was talking about. It was a sharp learning curve for me, maybe if I hadn't been learning stupid shit about Jesus, or how to work out the angle of a triangle (who gives a fuck what angle it is? And who does that for a living) I could have been learning about how engines etc work.