Parents should consider taking tablet computers off their children to ensure they get a good night's sleep and are ready for school, it has been suggested.
Dr Mary Bousted, general secretary of the Association of Teachers and Lecturers (ATL) said that mothers and fathers need to monitor their youngsters' use of the gadgets, amid fears that children are spending hours and staying up late into the night playing on them.
The union is due to debate a resolution at its annual conference in Manchester next week highlighting teachers' concerns about "tablet addiction" among pupils.
It says that symptoms of this addiction can include include pupils being withdrawn at school, lacking interest in other activities, being irritable, deceptive and performing poorly in lessons.
The motion calls on ATL's executive to draw together evidence on the problem and produce a factsheet for all education staff.
Speaking ahead of the conference, Dr Bousted said that tablet computers are "extremely empowering" and make technology accessible to many people.
"There's no doubt that they are being used more in schools but there are concerns that increased time spent on the screen, on your tablet, leads to far more sedentary and far more isolated children and young people," she said.
She added: "I don't think anybody in the debate is going to say 'let's go back to the 20th century', it's about how they are managed and how they are used and particularly about how they are used in schools.
"And perhaps there will be a debate also about the ways in which parents should monitor the use of tablets and computers at home."
Dr Bousted said that the resolution was likely to address the effect of children over-using tablets at home and the effect this has on their school work.
"In the past we have talked about not just the time spent, but the effect of typically violent games on young children and their behaviour, particularly in the playground. and we have talked about the need for parents to monitor not only the time spent that the child is on their tablet or computer, but also what they're actually doing, what programmes they are on, what games they are playing," she said.
"It's really difficult, but they do have to manage it. It's just like having a television in the bedroom, only its easier with a tablet, it's smaller. I have talked with parents about how difficult it is to manage. Because they are smaller you say 'turn your tablet off now and go to bed' and two hours later you go up and they're under the duvet still playing the computer game."
Dr Bousted said that tablet computers are easy for children to use and they can be playing games or using social media sites for hours at a time, rather than sleeping.
"My view is the only way you can do it is to take the things off of them," she said.
"My view is that if the child can't be trusted to turn it off when asked then take it off them."