please help I don't know what to do
My 12 yo son has had two girl best friends (we'll call them A and V) since they were babies, basically. We've become friends with their mothers over the years, and we let them have sleepovers at each other's houses quite often. They go to the same school, my son and A, and recently my son started coming home from school very down and irritable. I tried to find out what was wrong, and yesterday he finally confessed that for the past few weeks his classmates had been avoiding him, talking about him behind his back, and yesterday a classmate asked him if it was true that he had masturbated in front of A and V at a sleepover and had touched A while she was sleeping.
I know how this sounds, I was so fucking worried and I didn't know what to do. I asked him if it was true and he completely denied it, crying. I'm a psychologist and I always know when my son is lying, and I believed him.
I spoke with V's mother (who doesn't go to the same school) so she could ask V about it, and after talking to her, she called me to say that V had denied anything like that had happened. She seemed horrified and said that she was even the one who slept in the middle of the three of them and nothing happened. They just watched a movie and went to sleep.
After that, I called A's mother and told her the whole situation, to which she replied, "It's just kids being kids." (Are you fucking kidding?!) She knows her daughter lied, turning all the children against mine, and she didn't apologize or anything. I'm devastated. My son is still being bullied, and V isn't even at the same school to defend him or correct what happened. I don't understand A's mother's reaction, and I don't know what to do anymore.