A head teacher is taking children's computers and TVs from their bedrooms in an effort to improve behaviour.
Many parents fear children spend too long in front of screens
Duncan Harper, of New Woodlands School, which deals with pupils excluded from other primary schools in Lewisham, south London, said standards had risen.
Parents gave permission for him to enter their houses after he told them pupils were arriving tired and irritable every morning.
Mr Harper said stopping computer and TV use at night made a "real difference".
He has confiscated computers from nine pupils in four years. They are returned when the children's behaviour at home and school improves.
Mr Harper's methods have received the backing of Lewisham Council.
The mayor, Steve Bullock, said: "Education is about a three-pronged approach, involving schools, students and parents.
"The relationships between parents and schools in some cases has gone wrong and Duncan Harper is turning that around.
"When I was a kid, a message home to my parents would have had me quaking in my boots.
"The kids these days have so many temptations to use electronic equipment that they need more - not less - guidance."
New Woodlands, which deals with primary-age children excluded from mainstream schools because of behavioural problems, was recently rated "outstanding" in all areas by Ofsted.
Mr Harper, a head teacher for 12 years, said: "We decided about three or four years ago that a lot of children were coming in, very grumpy, very tired, irritable and getting involved in silly little disputes and not ready for learning.
"And when we looked into it a lot of the children had televisions, Playstations, X-boxes even computers in their bedrooms."
He added: "We will ring the parents and they will say 'that's great, that's fantastic, please come round'.
"So we go round, and that's the hard bit, once the televisions and the Playstations are out of the bedroom.
"When the children have earned it back, we say 'try and keep it in a central part of the house where it's a shared resource for the family where you can have normal disputes about what you watch and who plays what'."
One pupil, who had had his television confiscated, noticed an improvement in his own behaviour and, when it was returned, decided he no longer wanted it.
The British Dietetic Association poll of 3,000 school children found they spent a fifth of their time - or 2.5 months a year - on average playing video games, watching TV and using computers.
The Basic Skills Agency warns that too much television and a lack of family meals are damaging children's conversational ability.
Some four-year-olds threw tantrums in class because they could not communicate in any other way, it found.