Computers can help pupils do better at primary school, but can hold back teenage boys, who spend too much time playing games.
Research carried out for the Department for Education and Skills found that 16-year-old boys who were unable to resist the temptations of computer games did worse at school than their peers.
Girls tended to be more conscientious and use the computer for schoolwork, said academics at Leeds and Sheffield universities and research company BRMB.
The research was based on a survey of pupils in 12 schools, interviews with 111 children and analysis of the children's home use of computers and their attainment in national tests and GCSEs.
The report said: "The more time pupils spend playing computer games, the less time they may have available for other tasks, including homework and study.
"Some children reported pretending to their parents that they were using the home computer for educational purposes when they were actually using it for 'fun'."
The researchers said schools should encourage pupils to be more responsible in using the computer for homework.
Computer games were played every day or at least once a week by 61 per cent of boys, compared to 44 per cent of girls. This pattern of girls using the computer for work and boys for fun was already established by the time children were seven-years-old.
More than four in five parents of seven-year-olds said the computers helped their children learn useful things and less than a quarter had rules governing their use.
English was the subject which children were most likely to use computers for at age 11, 14 and 16.
There was a link between home computer use and an improvement in maths for 11 and 14-year-olds. There was also some effect on their progress in English and maths by 16.
Children and young people's home use of ICT for educational purposes: The impact of attainment on key stages 1 to 4 www.dfes.co.ukresearch