A government goal to get sugary drinks out of all schools by the end of last year appears to have failed.
The Health and Education ministries asked schools to allow only water and milk by the end of 2016. They have not done any work to see if the target was reached, but an Auckland University survey suggests it is a long way off.
Figures from the university's School-FERST study showed by term four just 10 percent of high schools and 35 percent of intermediate schools did not allow sugary drinks.
Primary schools were faring much better, but were still well below target at 70 percent.
Professor of nutrition and global health Boyd Swinburn, whose team carried out the study, said only about a third of New Zealand schools replied to its survey.
The Ministry of Education should be keeping tabs itself, he said.
"The level of follow-up, of monitoring... seems to be very weak.
"So it is not surprising schools, by and large, don't pay a lot of attention to it."
The ministry's deputy secretary of early learning and student achievement, Karl le Quesne, defended its lack of follow up and said he was keen to look more at the Auckland University study.
The goal was a "stretch target" and "aspirational," and while it was promising to see primary schools doing well, there was more work to do.
The ministries had provided policy and health advice to the schools to help them, he said.
Senior doctor and long time anti-obesity campaigner Robyn Toomath said if the ministries really want to make a change, they needed to back up their words with meaningful support.
"Schools have a heck of a lot on their plate and just a directive, with no monitoring put in place or no incentives or no assistance to achieve this, is probably going to fail in all but the most motivated of schools - who are probably doing it anyway."
Dr Toomath said the government should reintroduce regulations that forced schools to sell only healthy food.
Children at Holy Cross School in Auckland's Papatoetoe are allowed to drink only water at school.
Principal Bruce Young said the kids still loved fizzy drinks, but had learned that school was not the place for them.
"Now its just part of what happens at school, just like wearing a uniform.
"They know the rules - and sometimes they break the rules - but 99 percent of the children follow them pretty easily."
He said it was up to every school to make its own call on removing sugary drinks but he would encourage them to get do it.
The Ministry of Health said in a statement the real situation was likely to be better than Auckland University statistics reflected because the study did not include term four.