Others have high numbers of staff and students away because of the virus.
It's impacting both rural and urban schools but police said they couldn't give a definitive answer on how many schools are affected and which cities or towns are worst hit.
School principals say the Omicron outbreak is contributing to a lack of traffic wardens at schools.
Principals' Federation national president Cherie Taylor-Patel said, "everyone's coping with Omicron so systems are down at some schools or have to be changed every day".
She said numbers may be so low at some schools, "patrols aren't warranted or students are coming in at set times and staff are meeting them at the gate".
Taylor-Patel said "schools are doing all they can, in the situations they're in".
Local volunteer Aimee Harrison prepares to assist some parents and children to cross the road outside Parua Bay School. Photo / John Stone
She said she hasn't heard of any safety problems at the school gate to date.
Motorists are being urged to be extra careful around schools while some don't have traffic patrols.
Brake NZ director Caroline Perry said drivers "need to look out for children, especially during drop-off and pick up".
She said "kids are kids" so can do "unpredictable things" so slowing down is important, as well as being aware of hazards.
Perry said, "having that school patrol is an extra protection" outside schools.