Parents said exams were keeping children up at night

A poll of parents in England and Wales found 26% of 14 to 16-year-olds had missed sleep in the previous month.

Some 17% had done so because of school-related concerns, the survey for the Times Educational Supplement found.

Overall, 21% of the 500 parents of four to 16-year-olds interviewed said their children had missed sleep.

Bedtime suggestions

The biggest cause among the youngest age group was nightmares, while for the oldest it was academic pressures.

Only 6% said their children's school recommended how much sleep was needed, with 3% suggesting bedtimes.

The survey also found 68% of children had televisions in their bedrooms, with 34% allowed to watch after going to bed.

Some looked at more than two hours of programmes before going to sleep.

Meanwhile, 12% had internet access in their bedrooms.

The survey found that 99% were in bed by 11pm and 97% had switched off their lights by 11.30pm.

Commenting on tests stress, the Department for Education and Skills said: "Children sit just three sets of national curriculum tests during their 11 years at school.