Hi Thomas,
Another way to decide is to take some courses in whatever discipline(s) interests you. keep your options open/flexible...you will be a different person by time you start college...
I happened to find electricity in HS really interesting so I studied electrical engineering in undergraduate...while at college I found I could also take nuclear reacter theory...so I had a minor in that...it was totally unplanned. I had absolutely no reason to study that discipline but it sounded cool and seemed interesting...and my college had a nuclear reactor on site!
During my study of nuclear reactor theory, many years ago, I decided (a) materials will fail from exposure to radiation and (b) there is no way to dispose of nuclear waste so I figured the field would be limited, (c) the public would likely be afraid of it, (c) it was expensive. Nobody taught me that; it just seemed obvious.
Turns out most of the materials issues were solved, I think, over ten or 15 years, but nuclear waste and environmentalists killed nuclear power in the US for many years...it was accepted much more widely in France.
I took some extra math classes in undergraduate...turns out just a few more and I could have gotten a degree in math as well as EE...but I did not realize that at the time and my "guidance counsler" a MATH prof, never mentioned it! ? That was my second bad experience withj guidance counselers, so do not rely on them.
While in college I decided to go for a graduate degree in EE...I had never planned for that either...but I liked studying EE...that turned a Masters was enough school for me...and I needed to earn money...another unplanned event was that in graduate school I was given an Assistantship and I taught an EE lab to undergraduates there, then a senior EE lab back at my undergraduate college the next semester. When I interviewed for jobs, employers loved that I had already supervised people! (I had never even thought about that.)
I heard a radio talk show on artifical limbs this past week...prototypes are now being used on veterans that involve most of the skills discussed here..medical electrical,mechanical,robotics,etc,etc...that should be a rapidly growing field...I think MIT does work in that field...