Police officers were outside at least one school in North Canterbury on Thursday during drop-off and pick-up times.
The Herald understands at least one school reported the behaviour to police.
A police spokeswoman said they had been notified of the protests and were present to ensure the safety of people.
"Protesters remained outside the school premises and did not need to be removed," the spokeswoman said.
"We encourage individuals attending protests to conduct themselves in a safe manner and adhere to current Covid-19 red restrictions, which are there to ensure the safety of all."
Canterbury Primary Principals' Association president Sandy Hastings said it was "really disappointing" that protesters are "not considering the impact of their behaviour on our children".
"I assume they are protesting because they care about kids and yet their actions are doing a lot of harm," she said.
"If they want to protest, there are other places they can go.
"The Government are the ones who mandated vaccines for school staff, wearing of masks, and schools are doing the very best they can to support what they have to do and to make sure that our children can come to school and be safe and healthy and happy. So to have this happen at the gate is really disappointing."
Hastings said the actions create mixed messages for children and undermine the work of teachers and parents.
At least six protesters were photographed outside one school with signs.
"No long term safety data," one sign read.
"Remember thalidomide," read another.
Thalidomide was a popular form of sleeping medication, sedative and morning sickness drug in the late 1950s and early 60s. However, it damaged unborn children when taken in early pregnancy.
Police are asking anyone who may feel unsafe to get in touch with police, by calling 111 if the incident is occurring or 105 if it has happened.
Last December, a small group of protesters gathered outside Birkdale Intermediate as the children prepared to leave after their annual prizegiving assembly.
The protest was directed at the school's decision to allow its school to be used to film children for an upcoming vaccine campaign.
Police also attended, keeping an eye on the group and preventing them from going on to school grounds.