A lack of relief teachers in Northland has seen some class sizes double.
A survey carried out by Northland principals revealed a shortage of relief teachers which saw more than 90 classes across the region without a teacher because they couldn't find a replacement.
There were 415 teacher-absent days in one week alone last month and 92 of those days were left uncovered.
As a result, the principal stepped in to teach, but usually classes will end up doubling in size, meaning a classroom of up to 80 students.
"Rural schools are the ones that are finding it really difficult to get relievers, also our kura kaupapa, our Māori medium schools, there's almost no relievers available to them," Leanne Otene from Te Tai Tokerau Principals' Association told 1 NEWS.
Teachers across the country remain in a pay dispute with the Government which led to last month's mega strike.
Ms Otene says relievers are hard to get throughout NZ due to poor pay conditions.
"The ball is in the Minister's court to fix this problem urgently."