Jacinda Ardern was at Tuahiwi School and things turned sour when she left on Thursday afternoon.
Protesters lined up outside and screamed "shame on you" and "murderer".
Police were called to the scene and tried to disperse the crowd.
They yelled at police and chanted at media to "tell the truth". Young children could be seen among the crowd.
Ardern was at Tuahiwi School as it is part of the Government's Free and Healthy School Lunches programme, free period products initiative and has six learning support co-ordinators.
Tuahiwi School principal Melanie Tait-Pitama said she did not see much of the protest, instead she was keeping the pupils inside the school.
"What I do know is, it wasn't our school whānau up the front, they were able to get through, but it was protesters with no link to our kura.
"If there were tamariki who have seen parts of it, it would have been distressing but we are lucky most of the school is at the back of the property so I think at least 95 per cent weren't involved in seeing it."
It was the second time Ardern faced protesters on Thursday after she was heckled while making an announcement on a low-emission transport scheme this morning.
While standing beside an electric truck photo opportunity, a woman can be heard yelling "you are a traitor" at her.
By Georgia O'Connor-Harding
