By the time I was a junior in high school I had my choices narrowed down to Electrical/Computer Engineering, Computer Science, Theater Performance, and English Literature focusing on Creative Writing.
When I was a senior I decided I wanted to have the best shot at having a high-paying job out of college, and there was actually a glut of programmers on the market at the time, so EE it was.
I'd be delighted if my daughter could narrow it down to even the broad ideas I had early in high school, but she just doesn't know, and many of her friends do, which scares her. No matter how much we tell her she doesn't have to make any concrete decisions and just areas of interest would be helpful, she just can't get past her fears.
I think one of those personality profile tests might be good, not so much an aptitude test but rather something that helps determine potential career interests based on what you like (or don't).