Not really masturbation again, more of a blow job during school in the toilets.
So, my girlfriend works away at my dick, and I'm loving it, we're in a cubical and it's lunch time, the time where no one uses the toilets near Yellow (other side of the school, the one we are using). I'm letting out low moans, when suddenly, a bunch of my mates walk in. I shit myself, and pull her off my dick, and we both hide. I decide to let it carry on, however, and make her suck my dick very lightly and softly, so she did. And I came, right in her mouth.
After 5 minutes with her holding cum in her mouth, my mates left. God, scariest moment in my life.