"It mostly happens in the playground with the Year 7, 8 and 9 kids," he told The TES.
"There are usually two people or more doing it. One shoots the footage on their phone and then the other person goes up and slaps a student.
"They pick on the weaker kids. Those who get hit feel crap, but they usually try to act like nothing's happened.
"I'd heard people talking about happy slapping before Christmas but I didn't know what it was until it started happening this term.
"I haven't got a 3G phone, but someone showed me one of the videos where a boy, who looks like he was at my school, was sitting there working and another kid just suddenly slaps him round the head."
Ellie is a 15-year-old pupil at a Surrey secondary school. Last weekend she saw a group of teenage boys happy slap some of her friends.
"I was out in Walton-on-Thames with my friends having a laugh when the group started happy slapping my friends who are boys.
"They videoed the slappings and said they were going to send it to a happy slapping website. I didn't like the idea that there was a website to encourage this."
On youth websites, complaints by teenagers about happy slapping are posted alongside requests from others for copies of the latest videos.
One youth wrote: "Happy slaps are just for kids who are bored out of their skulls and if the Government built youth clubs or parks for them to hang out in it wouldn't have started.
"If anyone has a copy of happy slaps please send it to me."
Another said: "You've got to admit it's funny - the people's faces. It's not funny if old people get it, but it's not me doing it."
One of the teenagers said they had recently seen two girls in Year 7 at their school being slapped.
"The funny thing is they all run off and start crying," he said. "None of them have the guts to hit back."
Names have been changed