I got quite a surprise in the car last year, and thought I'd share it
I've always been open with my son about masturbation, and told him that it is best in private, it isn't something to feel bad about. In fact, I've encouraged him to do it, and if the opportunity arose, to do it with friends. Even so, he never talks about it, though I know he does it a lot.
Last year we took a family trip over spring break, and took my son's best friend with us. My son was 12 then, and his friend was 11. I kinda suspected they played around a lot, which I was glad of. Both of them go to a Catholic school, though we aren't Catholic, and on occassion my wife and I have discussed some of the teachings we knew he'd be exposed to that we didn't agree with. One of those was masturbation, which the Catholics teach is a sin, etc.
On the long drive, my wife got on the subject of some of those teachings, and landed on the topic of masturbation, telling the boys that there was nothing wrong with it and that they shouldn't feel bad if they did it. My son's friend then piped up, and said, 'Yeah, how could anything that feels sooooo good be bad? I love it!'
I was surprised that he said that, especially so enthusiastically, and looked back at him to see him smile and he gave me the universal up and down motion of his hand, illustrating masturbation. My son was embarrassed by his remark and didn't say anything, but the rest of us laughed. I said to his friend, 'You sound like quite an expert.' He replied, 'I sure am. Any time, any place.' He had a mischevious look on his face.
When we got to our desination (a small, two bedroom cabin on the beach), as I helped them settle into their room, I asked if they had enough privacy. My son didn't say anything, but his friend said, 'Yup; I don't need much for what I want to do!' Again he had that mischevious smile on his face.
Over the five days we were there, I noticed they went in the room and locked the door every so often, and I could hear rustling around and giggling, so I know what they were doing. Good for them!