One in five elementary school students is getting a daily caffeine hit from soft drinks and chocolate, keeping them awake at night and causing sleepiness in the classroom the next day.
A Murdoch Children's Research Institute study of students -- some as young as five -- from 22 Australian schools found 40 percent had sleep problems.
Academic Jon Quach and his research team found children were having trouble getting to sleep and were waking at night because of the caffeine they consumed. Sleep problems were also linked to children watching more than two hours of TV a day.
One in three children had a mild sleep problem and one in 10 a severe sleep problem, leading to poor child and parent mental health, Quach's study found.
Dietitian Lisa Renn was astounded to hear parents were giving their five-year-olds a daily jolt of caffeine via cola, sports and energy drinks and even chocolate.
"Some parents have lost perspective. It is lazy and neglectful parenting," she said. "There are plenty of quick and nutritious snacks. Parents need to be firm and say no."
Parenting Research Centre executive officer Warren Cann said some parents "would not think to make a link between what kids are drinking and watching, and their behaviour and sleep patterns."
"Pester power can be a factor. When kids really want something some parents don't know how to say no," he said.
Principals' Association Victorian president Gabrielle Leigh said kids being tired at school was a major problem.
"Children might not feel like breakfast if they are still hyped up, which makes them tired and makes it hard to concentrate," she said.
The study, to be published in an upcoming edition of Journal Of Child And Pediatric Health, found sleep problems included difficulty going to sleep, unwillingness to sleep alone, night waking and nightmares.