Watching TV, tablet or mobile phone screens before bedtime is bad for children's health. Researchers looked at studies on this. Ninety per cent of the studies found that screen time means children go to bed later. They have less sleep, and poorer quality sleep. Screens are small, so children look at them in bed.

Children need more sleep than adults. Pre-school children need up to 13 hours a night. There are three reasons why screens are bad. First, the light from screens makes children think it is daytime. Second, videos keep children's brains active, so they cannot sleep. Finally, children do not exercise, so they are not tired.