A boy has been sent home from school today for "not wearing enough pink" on Pink Shirt Day.

Today is anti-bullying day and to support the day people across New Zealand - including dozens of school students - have been wearing pink.

But the day of anti-bullying turned sour for an Auckland family when Helensville Primary School sent a boy home for not wearing enough pink.

The boy's mother Claire Lealiifano took to Facebook to say her son had been sent home to change.

Mother Claire Lealiifano posted that her son was sent home from Helensville Primary School (pictured) after his teacher said he wasn't wearing enough pink. Photo / Google

Students were told they could wear pink in support of the day or they could wear their school uniform.

The mum said her sons looked for as much pink clothing as they could find.

"Apparently what he was wearing wasn't good enough. So the head of the year sent him home to get changed without checking I was home," Lealiifano said.

She said other children at the school were not wearing pink and wanted to know why her son was singled out.

She ended her post with #bullyingisnotok

The boy's parents met with the school principal in the afternoon to discuss the incident.

Lealiifano said the principal said the boy's T-shirt was pink enough and said the teacher was wrong to send him home.

The school is investigating.