Prior to his attempt, the World Association of Benchers and Dead Lifters World Record dead lift for a 12-year-old was 236lb, set by an American youngster.
Nicknamed Little Arnie after musclemen Arnold Schwarzenegger, Kyle now trains in the gym four times a week and can shift 600lb (272kg) with his legs, 309lb (140kg) deadweight and bench-press 200lb (90kg).
When he is not training, Kyle enjoys playing with his school friends at Grace Academy where his favourite subjects are History and PE.
His remarkable strength puts him at a huge advantage in Rugby - not to mention shot-put and javelin.
Kyle said he hopes one day to become an Olympic weightlifter and bring gold back to Britain.
He said: "I just want to be as muscley as I can be.
"Hopefully one day I can train in the Olympics or compete in the World's Strongest Man but failing that I'd like to be a professional bodybuilder like my dad.
"Other kids my age hang around the streets I like to train.
"It feels sensational to have broken a World Record, it's not something many 12-year-olds can say they've achieved.
"But this is just the beginning I want to keep breaking records and setting a new World Record every year if I can."
Kyle's World Record attempt was held in aid of The MS Therapy Centre in Coventry, which offers care and support for people with multiple sclerosis.
His father, John, said: "Kyle is so big for his age, sometimes I forget he's only 12.
"He can't even cross his legs because the muscles in his legs are so big, he eats us out of house and home and he's almost outgrown his school uniform, we're going to have buy him men's shirts soon.
"But he just loves training, he'd be in the gym every night of the week if I let him, but we have to make sure he doesn't overdo it."
A former professional bodybuilder, John, 44, has been weightlifting since he was 18 but said it won't be long before Kyle overtakes him.
He added: "I give it a year and Kyle will have beaten my record, his strength for his age is just phenomenal.
"The first time I realised just how strong Kyle actually is, was when he was 11.
"He was leg pressing in the gym and the whole gym came to a standstill and everyone just stared in amazement as he pressed 260kilos, it was unbelievable."