This happened to me when I was 13 years old. I attended a catholic school and the teachers were very strict. The was a boy in my science class that sat accross from me. He was tall and kind of skinny and his name was Phil. I noticed that Phil was constantly looking at my legs. It was a bit uncomfortable but I thought that is just what boys do.
Well, one day we were both assigned a science project together and we stayed after school to research our topic. Phil was acting real nervous and jittery and after about 15 minutes, I asked him what was wrong. He nervously pulled his hands away from his crotch and I saw this huge bulge. He said he had a hard on and couldn't help it because it happened every time he saw me. I was really surprised and asked if it hurt and he said no but if he could cum he would feel better. Now, at that time I knew little about boys and penises only what we learned in sex ed. I asked him what he should do and he said 'jack off.' I said 'okay, whatever.' I had never seen a real penis before in real life and I asked him how do you jack off. He said if I wanted to, I could watch him and he would show me.
We went down the hall and into an empty room, my heart was pounding. He pulled down his pants and instantly his huge penis popped straight up. It was gigantic and when I saw it, I got a tingle in my vagina. I watched as Phil pulled the skin up and down with a tight fist as his big balls bounced beneath and I could feel a wet spot between my legs now. I asked if I could touch it and he said 'please do.' I tried to wrap my hand around it but could not quite fit it all around because it was too big and it felt so hard. Then I put both hands around it and there was still a lot of penis sticking out. He showed me how to jerk it up and down and after about 4 jerks, his head rolled back, he moaned and shot thick streams of cum everywhere. It was all over my skirt, my blouse and in my hair.
I got really mad but he said he couldn't help it. I had to use my socks to clean it up before returning to the other classroom. The next day Phil told me that his parents would not be home after school for a few hours and asked if I could come over. He said he wanted to put a finger inside me and make me cum too. I said it would be all right as long as I could jack that beautiful dick off. We continued this mutual masturbation for over a year. What a great time!