I have to say I disagree with many here. There is a difference between touching someone's breasts and genitals, and touching other areas like arms, shoulders, thighs. I have close friends or family where it might be appropriate to touch places like arm/thigh, eg when comforting when they are upset, I don't think it's necessarily sexual. Breasts, bum etc is different, off limits outside romantic relationships.
I have no idea the full details of the boy in the story and dont want to get into an individual situation. There are definitely some sleazy guys out there who have absorbed horrible messages about consent and how girls want to be treated. But I also worry that we are playing down the responsibility of the girl to say "stop" or move away from someone or remove their hand or whatever.
I think we need to resocialise our girls as well as our boys. Its like when there are threads on mumsnet where people say "the neighbours kid keeps coming over every day and its driving me mad" but they haven't got the courage to actually say no to the child or parent. There are loads of threads of women saying basically some variation of "I dont like this thing which someone else is doing but I don't have the confidence to tell them". I see leg-touching as the same thing: tell the boy to stop, don't just put up with it and then complain to someone else later. If the boy carries on after being told to stop, then that's when it becomes inappropriate.
When I was young, guys would sometimes touch girls leg or put arm round shoulder as a way of making a move. If the girl's not interested, she moves away or remove the other persons hand or whatever. If the guy keeps persisting then obviously that was a problem, but I think its ridiculous if touching someone's thigh is now assault.
I genuinely wonder if it's possible to "get together" organically nowadays outside of online dating, if people can't gradually "test the water" in an appropriate way (not just grabbing someone's ass or breasts, but maybe touching arm or something). Do people genuinely have no physical contact at all and then comevout and say "can I kiss you/will you be my girlfriend" because the only time that ever happened to me was when i was 12/13 and it was gross.
Sorry if thats an unpopular opinion. FWIW, I am the mother of teenage boy and teenage girl.