Violent computer games damage the "tender young minds" of children, a teaching union has warned.
The Association of Teachers and Lecturers (ATL) raised concerns about the negative impact of children spending hours a day playing computer games that are inappropriate for their age.
The warning came as a survey found more than a quarter of parents say their child gets less than half an hour of physical activity outside school hours.
ATL members are due to debate a resolution at their annual conference in Manchester next week which says some computer games have a negative effect on very young children.
It calls for the union's executive to commission research which will allow it to lobby government for the introduction of "stringent legislation" on computer games.
Speaking ahead of the conference, ATL general secretary Dr Mary Bousted said: "I think what we are talking about, first of all, is the amount of time children spend locked in their room. The fact that children spend hours locked in their rooms playing computer games, which means they're not interacting, they're not playing and not taking exercise."
Dr Bousted said speakers to the motion are likely to say that parents are ignoring age restrictions of computer games.
"Of course, they're extremely difficult to enforce, just like films, like TV," she said.
"It's about reminding parents and carers that they have a very real responsibility for their children and that schools can't do it alone.
"If they're up to 12 or one o'clock playing computer games, and coming to school exhausted, not interacting with other children, that's not good preparation for school, and not good preparation for life."
A survey of 1,000 parents, commissioned by the British Toy and Hobby Association,has found that 28.2% say their child gets 30 minutes or less of physical activity after school.
Just 5.3% of parents said their child gets more than two hours of exercise outside school, while 14.5% said they get between an hour and an hour-and-a-half.
Almost half of those questioned (45%) said their child should get an hour or more of exercise in a day.