A Cambridge University study has found that an extra hour of watching the telly, playing videogames or faffing about on the internet in Year 10 will knock down GCSE results by a couple of grades on average.
According to the BBC the study involved 845 kids in Cambridgeshire and Suffolk, monitoring them at 14 and comparing their GCSE results aged 16.
To control for other factors, pupils heights and weights were also monitored, and the kids had to wear physical activity monitors for five days (including a weekend). Apparently they were all given a survey and asked to detail the amount of time they spent on homework, reading for pleasure, physical activity, watching TV, playing videogames and "non-homework time" spent online.
Interestingly, the results apparently found that the kids who spent an extra hour on homework and reading did better than their peers, but there was no link between physical activity and academic success. Each extra hour of screen time knocked their grades down 9.3 GCSE points (whatever they are) - which translates to slipping a grade in two subjects.
The study appears to be annoyingly robust, having been published in the International Journal of Behavioural Nutrition and Physical Activity - so this is just more ammunition for parents arguing with their kids about doing their homework. [BBC]