A major American study has found that sleep deprivation is a significant factor in lowering the achievement of school pupils in 50 countries.
It found that New Zealand has the second-highest number of sleep-deprived students behind the United States.
Researchers at Boston College compared the results of 900,000 primary and secondary students in maths, science and reading with information on how much sleep they'd had, the BBC reports.
The study found that pupils who missed out on sleep are likely to under-achieve compared with their well-rested classmates. It turns high-achieving youngsters into sleep-starved average performers.
Sleep researchers say there is a particular problem with the night use of computers and mobile phones with the light from the small screens disrupting the natural sleep process.