None of the posts in this thread are solid advice in my opinion. You guys sound more like frustrated guys who feel they need to "make up for lost time" after reading a few pua books.
You should do whatever you want to do. And that not only goes for high school. If you want to be in a relationship with a girl you like: do it. It is very rewarding.
Don't run around telling young guys not to engage in anything 'serious', just because you probably won't see the girl in a year's time. Because honestly: you NEVER know how much the girl you're in a relationship with will mean to you in a year, let alone FIVE years.
Have relationships....I dont give to shits, all im saying is don't waste your time with some girl who's playing with your head when you could be out being young, having fun, ect ect....
Could you marry your high school sweet heart? yes....but lets be honest the odds are slim! plus this is a PUA forum not the "Disney fairy tail love" forum lol The reality of the situation is that 99% of these kids are going to get their heart broken, be bitter, and waste months trying to get back with some chick who they wont care about a couple years from now.
IMO your young! go have fun! be young, you have no idea what you want in life yet! If you told me what I wanted at 17 it would be very different then what I want now at 25, and at 30 im sure it will change even more!