Interesting way the O.P. worded her question, because there is a subtle, and sometimes sad difference between having sex and getting off.
When I was in elementary school I had a neighborhood friend who happened to be a girl. Her name was Tina. We were in the same grade, but because of our birth dates I was almost a year older. We spent a lot of time together until the end of 6th grade; this was back when jr. high started with 7th grade. By the end of 6th grade Tina had blossomed quite quickly into one of those hothouse child-women with huge breasts, an hourglass figure, and an interest in guys who drove cars, and not me. I had discovered masturbation and I knew we were both changing, so I didn't feel abandoned, but I missed her company. South Seattle was a relatively small community in 1959, and from time to time "older" guys talked about how hot and how easy she was.
In late summer I was at the beach when Tina walked by with a couple friends. She came over and started talking to me about old times. I couldn't help but notice how she looked in a swim suit, and was happy when she took my hand and suggested that we go for a walk into a small grove of trees. We stopped and she suggested that I kiss her. I did, only it was apparent that she had a lot more experience than I did, and I was trying to adjust my penis to keep my huge erection from touching her. After a couple of kisses she reached inside my trunks, grabbed me, and I just went off, squirting all over the place. She smiled at me and wiped her hand and said that these things happen. I was totally humiliated, excited, confused, and had about ten emotions raging around. She walked back to her friends.
School started; I saw her a couple of times in class, but she left school before the end of the month. There were a lot of stories about her. Six months later I was walking near the local home for unwed mothers and saw her a block away, hugely pregnant, with several other "bad girls". She saw me and turned away, and we never spoke again.