It's okay to not have kissed a girl being in high school, although getting some experience with women wouldn't hurt, it will aid you in being more confident. Just think you can still possibly have that first kiss with someone you really care about and have a long term relationship with.
Being a guy if a girl is willing to hang out with you alone that's a good sign she likes you and is willing it be intimate. When I was younger like 13 I would have girls like me and we would be in a relationship but I didn't know how to put the moves on them. Obviously nothing happened in those relationships. With lot's of women or girls you have a window so to speak where their attracted to you and if u don't put the moves on her she'll lose interest.
I read somewhere there's a test to see if a girl wants you to kiss her, where you play with her hair, looking into her eyes then look at her lips. I've personally never used it. I'f I'm alone with a girl I like often I'll put my arm around her and kinda cuddle not before long I'll kiss her and then things progress.
Kinda off topic but some women put up some resistance, which they want you to fight through, it's almost like a test to see if you're persistent enough, to put effort in and not just give up quickly. In some cases it's largely a way for them to avoid feeling easy while you put the moves on them. You gotta be careful though not to overstep with someone who isn't willing.
For example in 2008 I saw this girl and I watched a movie over at her place, in her room, she kinda did the resistance move on me, I didn't try to go all the way with her but later she told me she would have and wanted to go further with me, despite me not feeling the full green light vibe if you get what I'm saying.