School principals in Waikato say a generation of "P babies" is entering the primary school system and causing huge problems for schools.
Six principals have met to discuss the problem of babies born to mothers addicted to methamphetamine, which they say will only get worse.
John Cubitt, principal of Pekerau School in Te Awamutu, says schools have noticed a growing trend of children as young as five being uncontrollably violent.
He says other children are arriving at primary school unable to communicate verbally.
Mr Cubitt says principals fear the children have inherited the problems from their mothers' methamphetamine abuse and he believes it could be a nationwide problem.
He says other schools in Waikato have also noticed the trend, which is particularly evident in lower-decile schools.
A researcher looking at the impact of the use of methamphetamine on motthers' foetuses and infants is cautioning against using the term "P-babies".
Trecia Wouldes, a lecturer in psychological medicine at the Auckland School of Medicine, says the children's behaviour could also be the result of the abuse of other drugs or alcohol.
However, Dr Wouldes says principals have a right to be worried because more women are using drugs, and P appears to be easily accessible.
The Ministry of Education says there are options available to schools that have children with behavioural problems.