The Attendance Service has investigated 16,771 new cases of serious truancy in the first half of this year.

During the same period it resolved 12,726 cases - nearly half of them, because the child in question was found to be already enrolled in another school.

The new cases included 9838 students who were removed from their school's roll and classed as "non-enrolled" after being absent for about 20 days.

The remaining 6933 cases were "unjustified absence", essentially persistent truants.

The number of new non-enrolled cases opened in the first half of 2022 was close to the 10,727 cases opened in all of 2021.

The Attendance Service closed 7877 non-enrolled cases in terms 1 and 2, half of them because the children were found to already be enrolled at another school, while a quarter were helped to re-enrol by the attendance service, and 13 percent turned 16 and could legally leave school.

Nearly half of the 4849 "unjustified absence" cases closed in the first half of the year were closed by helping children return to school.

More than a quarter of the unjustified absence closed cases, 1284, were reclassified as non-enrolled, and 13 percent, 646, had already returned to school.

The Education Ministry says more non-enrolled cases were opened in term 1 than in term 2, which it attributed to the covid-19 Omicron outbreak.

It says fewer cases were opened in the second term and more cases were closed, which was a positive trend.

"As the country moved away from the traffic light system, as well as mask mandates being loosened, non-enrolment resolutions were easier," it says.

Principals' Federation President Cherie Taylor-Patel says primary school principals were worried about the relatively high number of families that had "gone missing" in the first two terms of this year.

"Principals were really concerned about students that had disappeared from their school that they didn't know where the families had gone," she says.

She says the illegal occupation of Parliament grounds and related protests increased some people's distrust in society and that prompted some to take their children out of school.

Taylor-Patel says recent efforts to encourage families to get children back to school appeared to be working.

"There's been a really big focus on getting students and families re-engaged in school and it's been really successful in a lot of instances," she says.

Figures for the full 2021 year showed most students referred to the Attendance Service had not been referred before but a small number, which was redacted, had been referred six or seven times.

About a fifth of the non-enrolled and a quarter of the unjustified absence cases last year were for students who last attended a decile 1 school and more than 60 percent of the cases involved Māori students.

This year's government budget included a boost of $1.5 million per year to increase Attendance Service providers' capacity.

- John Gerritsen/RNZ.