Im 16, and in the past three months I've stepped up my game to a completely new level. Here's what I've done and seen work at a high school level.

-Negging works. If your negs do anything other than make her giggle you're doing it completely wrong and you're not negging. In fact, from whats worked for me, i think it should be called teasing or being playful.

-Join a sports team. Whenever I say I'm on the varsity wrestling and football team (no big feat, our school is tiny), girls immediately go "Oh my God! Thats so cool!" and its probably the best DHV for highschool.

-Work your way up through what you've got. I used to hang out with all the nerdy losers. I worked my way to basically being their "leader." Then, i moved up to the lower "ranks" of the nerdy-kids-who-hang-out-with-girls group. Once i was on top of them (and joined sports) i was accepted into the normal kids group. Now I've moved up to into the cool kids group. Social ladder in highschool is crazy important.
The same applies with girls. Social proof is huge. My very first girlfriend was pretty ugly, but she was obsessed with me. Her friends, who were better looking, always heard about how "awesome" i was. So, i moved on to her friends. And on to their friends. And then over into a hotter more popular group. Just keep going. Climb that ladder!

-Text and phone game is huge! Send messages that could possibly have sexual connotations. If she's established you as kind of a teaser, she'll just giggle, but the thought still runs through her head. And if you do it right, it works wonders.

-Girls are usually really nice about rejection. They'll say "Lets just be friends. Ok?" and they'll still hang out with you (if you're not creepy).

-Kino escalate fast. I recommend reading DiCarlo's Escalation Ladder. I've used it dozens of times now, and it has never once failed me.

-Be funny. I don't really know how to explain this other than be confident in everything you say. Don't be the kid who makes jokes in class that would be funny if the funny kid had said them. Watch that funny kid and try to copy him.

-Speak alot, with confidence, and at the right pace. I learned this from a friend who talks nonstop, says alot of things that aren't funny, and he says the stupidest things I've ever heard anyone say. But he gets TONS of hot chicks. How? When he talks, its confident and no one feels awkward when says something not funny or stupid. So, when he says things that are funny (about once in every 5 attempts), girls forget the other stuff and only remember that he's hilarious. Because he's constantly talking, he seems like he's in control, even though none of us guys ever listen to him.

-Throw parties if you can, or at least call everyone together for social events. Throwing parties for UFC fights and bonfires seriously helped me climb the social ladder.

-Get a reputation as kind of being a "Badboy" while still being nice and playful. You don't need to vandalize stuff or smoke crack (i recommend you don't). I realized this when i showed up to school with a bruise that looked like a hickie. Every girl i talked to noticed, and all i did when they asked what happened was say "Ohhh, i just got hit with something." They asked what and i said "It was like a pole or a bat or something." The girls immediately assumed it was a hickie. I didn't act like i was hiding anything, and it wasn't a big deal. The responses in body language from them was incredible. It was like they all of a sudden realized I was sexual and that they could be sexual with me.

-The last thing i learned is that after you've established attraction (my definition is that the girl likes you, and thinks that you consider her special) super cheezy shit works wonders. Stupid forwards, cheezy love poems, all that stuff. In highschool, girls apparently think that they fall totally in love every time they like a guy.

So ya, thats my take on highschool game so-far. I'm still pretty new, but the results I've gotten from the past few months have been incredible. Hopefully this helps someone. Good luck guys!