Pupils sleep in foldable chairs under their desks at a primary school in Hebei province.

Simply by lifting the desks and pulling the chair arms, students can lie down to nap in classroom at a primary school in Handan City, north China’s Hebei Province.

Photo taken from people's daily china fb page

Children who are forced to have long naps at preschool could develop sleeping problems later on, new research indicates.

Sleep experts say some older preschoolers no longer need naps, and the disrupted night sleep caused by them could trigger a range of serious health problems if it persists in the long term

Study author Sally Staton said her research raised important questions about the impact of mandatory long nap-times on child health, given the number of children who attended childcare before starting school.

"Insufficient night-time sleep in young children significantly increases the risk of poor health and developmental outcomes, most notably behavioural problems," she said.

The study of nearly 170 children aged between four and six found that attending a childcare centre that enforced mandatory nap times of longer than an hour was linked to children getting an average of 24 minutes less each night.