I have 0 social skills with kids my age?

Look I never faced reality until now, and it hurts, badly. I never talk in school...Never before. Today I asked a kid my age (15 Freshmen) for what was the homework. Then out of nowhere, even the new kids tell me this, that I am short, unathletic, stupid, and bad at everything, suck at life,and have no social skills. I've been told nasty things, but nothing of this sort. I realized it hurt so much because well it's true. I'm sick of people feeling pity for me. And the bizarre part of this conundrum is that I get along with adults fine. To make friends I tried listening to someone, being nice and honest. It dosen't work. So how do i start a conversation and keep it going? Give examples and different scenarios.