This.
Advice to kids/teens: Learn how to build stuff. Learn how to fix stuff. Learn how to do things, real things, not video games. Get an understanding of how and why things work. It almost doesn't matter what it is, it's best if it's something that captures your interest.
The question is fairly wide, but since engineering is mentioned a fair bit, here is an take from someone who works in the industry. In tech, we work closely with the University of Waterloo, among other top schools and hire anywhere from coops to undergrads to post-docs and researchers. So what am I looking for when hiring people and how important is education?
For engineering, you need a degree. A diploma is a tough sell, but plausible and self-taught is almost non-existent for top firms. That said, one of the best coders I worked with actually dropped out of highschool, but those guys are very rare. B.Eng is great, P.Eng is better, but M.Eng or Phd makes hardly any difference. 99% of the time there is no replacement for formal background in engineering, particularly in software development (despite what most people think). That said, when I look at transcripts, generally kids in the 90+'s avg. are not the kids to hire. Great at tests, terrible at real problem solving. Of course they will get a few technical questions in the interview to solve a simple real world problem, but the more important question is the first question I generally ask: What do you do for fun?
Why? 1.) it breaks the ice and 2.) it tells me a lot about someone. If you watch netflix and surf snapchat all day, it tells me more about you than grades, references, or the like. I asked one kid "Why do you want to be a software engineer?" The response: Because my mom and dad said I should. Not great. However if you tried to build a rocket with your friend but failed, that's much more interesting. One kid I had last week tried to create a machine vision robot that could play mario bros. Super cool. I can teach skills, I can't teach ambition, drive or passion. Success in this business is about drive and persistence. Did you re-write your algorithm 5 times and loose a night of sleep because something about the design was bothering you? or did you just click submit and move on never to look at it again?
Trades were also mentioned. I know a few people in that business who can't find people willing to work. Good money, union or otherwise. No drive in the kids, or they don't even show up at all. It's the same deal, show ambition and be accountable. Also show you want to earn your next ticket. e.g. if you're a gas fitter, also get your electrical or refrigeration ticket, it only drives up your value.
Formal education requirements have increased in the past decades, and will continue to do so for most work. Why? liability. This also means a premium on the work (higher barrier to entry). It will take effort, but it does pay off.
edit: Oh, and if the thing you're doing in school isn't a job title, you are probably wasting your time. It's hard to hear, but it's also true.