In high school, I had no idea I wanted to be an engineer. Now, it's amusing how what I did (and didn't) learn in high school affects me. Take math, for example. In Calc BC, someone once asked for a "real-life" application of the concepts we were doing. So, my math teacher comes up with this ridiculously hard problem about a piston and its rate of movement or some such. The conclusion was that no, you don't use advanced Calculus unless you're doing extraordinarily advanced physics.

Then I came to college, and realized "Oh god, I'm a mechanical engineering major, I have to be able to solve that piston problem."

On the other hand, all that doodling in high school has given me the skills to draw really pretty schematics. XD