Sounds like you're serious! Okay! Well, as far as your schooling goes--take ALL the science classes you can. This also goes for math classes. They go together. When you get to high school, continue this trend. Hopefully, that will include physics and calculus classes.
Over the summers, see if you can get into summer science camps--and eventually even work at these camps as a counselor in the summers. Also, get buddy-buddy with your science teachers (after they get to know you and your work ethic) and ask them if you can TA for them (my school only allows juniors/seniors to TA for teachers but it's incredibly helpful). Also ask if they know of any programs you can get into or people that you should meet.
Eventually, you're going to want to observe science teachers in the classroom after you leave high school. It's hard to see the other side (the teaching side) and fully understand it until you leave your high school life/world behind (check out both middle and high school classes). Look into colleges and universities that have strong education and science departments. If they do their job to help you, you'll be in and out of college in four years--and with two degrees.
I do want to note that it's not a bad idea to keep your mind open to other things you love. Take fun classes in high school (while they're free to you
and see what else interests you. Even if you're set on teaching science, you're going to need a break every so often. So take some time to find other things you enjoy. Good luck. Science rocks.
Note: When you go to observe science classes, go to different schools. Each school (and district) is run a little differently. Get a feel for it. You'll have an even better idea of what you like when you student teach. Science is going to be a big need area very soon, so when you're ready, you could have some great choices to choose from.