Not gonna happen bro. I am sorry to burst your bubble. Unless your HS team is real real bad, or has a shortage of students trying out.....your not going to make it.
Hitting a baseball is one of the hardest things to do in all of sports. Your using a round bat, to hit a round ball that is being projected at you at a very fast rate of speed on multiple axis. It is very hard. Hence when a good batting average (.300) is considered great. That's getting a hit 3 out of 10 times. Lots of failure.
Most of the good pitchers in high school will be able to throw a curve ball, fastball, change up. Which makes it even harder then little league where it's mostly just fast balls.
Unless you have a true god given talent, it's not going to happen man. Most kids in high school that play ball, have been playing ball continuously since they were little kids.