This happened when my best friend and I were seniors in high school. It was towards the end of the year and we both wanted to do something we wouldn't forget. There was a school-wide assembly coming up, so we both decided we would bring our vibrators and secretly masturbate through the entire thing and see who could have the most orgasms.
Right before the assembly was supposed to start, we slipped into the bathroom, pushed our vibrators in and made our way back to the auditorium. We sat next to each other in the back and eagerly waited for it to start. Luckily, there were a lot of empty seats so we didn't have anyone sitting around us. As soon as the lights dimmed, we both quietly reached into our pants and twisted them on. Instantly, I bit my lip to stop from moaning and blowing our cover.
After only a few minutes, I could tell she was about to cum. Since we have masturbated in front of each other many times before, I know that her toes curl whenever she has an orgasm. A few seconds later, I glanced at her feet and her toes were gripping the bottoms of her sandals. She then let out a soft sigh and relaxed with a smile on her face. It was only a few minutes later that she had another silent orgasm. Watching her caused me to go over the edge, as my hands gripped the armrests, I held my breath and exploded with an enormous orgasm of my own. I knew I was still behind, so all of my thoughts focused on the throbbing inside of my vagina. Time went by and we both had more orgasms. Towards the end, I could tell that she was about to have a big one. Her flip flops were kicked off, she pulled her knees together and her toes spread and curled. Seeing her in such pleasure made me cum yet again.
When the assembly ended, we both caught our breath and quietly turned off our toys. After we had collected ourselves I found out that she came nine times while I could only manage six. Still, that's not a number to be ashamed of. Luckily we both wore dark pants and long shirts that day because we were completely drenched. When we stood up, our knees were so weak we had to prop ourselves up with the chairs in front of us. Walking back, a friend saw us and asked why our clothes and hair were a mess. We glanced at each other and told her that we both fell asleep. Little did she know we were sitting a few rows behind her having the time of our lives.