This means principals could face harsh penalties, including fines of up to $600,000 or five years' imprisonment.
As a result, some principals fear higher risk activities like outdoor education and camps could become a thing of the past.
Rotorua Principals' Association president and Ngakuru School principal Grant Henderson was not planning on changing the way his pupils used the school grounds.
"As a principal I am worried about the worst case scenario but ultimately it comes down to our philosophy of education.
"We're not going to stop kids climbing trees, but we do reinforce that they need to know their limits and not climb so high that they can't get down.
"If I was to stop our pupils climbing the trees around the school, I might as well get rid of the playground as well because they are about the same height."
John Paul College principal Patrick Walsh said the new act was particularly concerning to secondary school principals.
"Teenagers do not process risk the way an adult does and that means they are more likely to do something that could get them hurt. When schools go on camps and take part in outdoor education, there is more potential for something to go wrong than if they were learning about it in the classroom so it does raise the question of whether those activities are worth continuing."
He said the new act also had the potential to put teachers off taking up principal positions for fear of personal liability.
Otonga Rd Primary School principal Linda Woon said school camps were already becoming fewer and shorter as a result of health and safety requirements.
"You can't wrap children in cotton wool but we are seeing camps get more expensive, shorter and schools going on fewer of them because of the time, effort and cost that goes into the risk analysis.
"With principals being more liable if an accident happens, it does concern me what the future of Education Outside the Classroom (EOTC) looks like."
WorkSafe communications general manager John Tulloch said the fear EOTC could diminish with the new act was unfounded.
"The new law doesn't create new risks - the law might be changing but the risks have always been there. Schools are already managing risks for the likes of camps, making use of guidance from the Ministry of Education."
He said the new act would not stop kids going on camps and "experiencing the usual playground rough and tumble that is a part of growing up and going to school in New Zealand".
"Talk of banning kids climbing trees, going on camps or making farm visits is a massive overreaction. The new law is about helping lift New Zealand's workplace health and safety performance."
