Teachers are physically restraining children to stop them hurting themselves or others more than 130 times each month, Education Ministry figures show.
Since the start of August, schools have had to notify the Ministry of Education every time a teacher physically restrains a student.
Between 1 August and 25 October, 186 schools made 423 notifications, all involving the use of force because of a serious and imminent safety risk.
It said more than half the cases involved children with recognised behaviour problems.
Twenty-three of the reports came from secondary schools, 79 from special schools, and 321 from primary schools.
The ministry's deputy secretary sector enablement and support, Katrina Casey, said physical restraint was a serious intervention and should only be used as a last resort.
She said the notification system helped the ministry support schools and it also protected staff by ensuring there was a written record of each event.
"It's early days yet to assess what we've gleaned from the information - the new rules only came into effect in August this year - but insights from the data include the prevalence of physical restraint in our schools," she said.
"For some context, about 10 incident reports a day are sent to the ministry for follow up. However this represents a small percentage of the approximately 800,000 students and more than 2500 schools in the school system."
'Am I at risk of losing my career if I intervene?'
The Principals' Federation's Whetu Cormick said the figures probably understated the number of times teachers and principals were stepping in.
"We do hear from our colleagues that there are some misunderstandings on what needs to be reported. We've also heard that some colleagues are unclear on what is restraint and what is not restraint and also what needs to be notified to the ministry and what doesn't need to be notified to the ministry."
Mr Cormick said new rules about when teachers could legally use physical force also meant teachers were less likely to intervene, so the ministry's numbers would not reflect how often children were putting themselves or others at risk.
The president of the Post Primary Teachers Association, Jack Boyle, said the union's members had indicated new guidelines and requirements around physical restraint were making them think twice.
"Teachers have always thought twice about it, but now what... some teachers will be thinking about potentially is not 'is that young person at risk of harm?' but instead there's a backstep 'am I at risk of losing my career if I intervene?'," he said.
Tai Tokerau Principals Association president Pat Newman has been outspoken about the behaviour problems facing teachers.
Mr Newman said the ministry was requiring notifications about trivial incidents, such as breaking up fights between five-year-olds.
"I have no problem notifying the ministry if it's something serious, but I think they really do need to look at what is serious.
"It's brought another level of fear into schools and into teachers about what are going to be the consequences of keeping children safe."
But Children's Commissioner Judge Andrew Becroft said monitoring the use of physical restraint in schools was important.
"Although some might be classed as reasonably short-term or even low-key or trivial incidents, I think it's important for public confidence and in a free and open society for these sorts of figures to be available, and to be available for interrogation and available for discussion."
Judge Becroft said teachers had a clear legal basis for when they could use physical force.
"It's proper that that provision is used as and when appropriate and when needed. It's there for a reason so I'd hate to think teachers felt that if they were legitimately exercising that power somehow they would be criticised.
"We trust teachers to do that."