Schools close for holidays at the end of the week and principals are worried that severe disruption from winter illnesses and Covid-19 will be even worse when they reopen.

The current term has seen many schools cancel classes or even close altogether due to staff absences, and student absence rates have also been high.

But Covid-19 numbers are rising and principals warn that illnesses usually peak in the third term.

Whanganui Primary Principals' Association president Linda Ireton says, after a good start in May, attendance nose-dived, sometimes sitting at just 60 or 70 per cent for some of the area's schools.

Principals are hoping the two-week winter holiday that started at the end of this week would give everyone a rest and maybe even slow the spread of illnesses, she says.

"I hope that for kids it gives them a chance to recharge. Our kids are tired. The winter terms are always hard for children so the holidays will be fantastic, give a chance to recharge their batteries and hopefully break that communication of the viruses between kids and staff," she says.

But some principals are worried things could get worse.

The principal of Randwick Park School in Auckland, Karen McMurray, says based on past experience term three will not be any better, though it's possible the pattern of winter illness had changed this year.

"Historically term three is the most challenging term that we have to deal with as far as staffing goes and the lack of relief teachers available," she says.

"Hopefully we've had term three early and we can look forward to term three being a little bit more smoother sailing."

McMurray says finding relief teachers to fill in for sick staff has been almost impossible this term and her biggest challenge going into the holidays is filling vacancies.

The school was advertising three teaching positions, including two temporary jobs to cover for staff returning to their home countries for the first time since the pandemic began, she says.

"We're very, very happy to support them to do that but in the meantime finding people to replace them has been near impossible. I've advertised widely across the whole of New Zealand and at this stage we haven't had any suitable applicants."

Ōtāhuhu College principal Neil Watson also expects term three will be just as bad as term two, if not worse.

"Traditionally probably worse with the winter flu season and the colder months, August is pretty bad."

Teaching has been disrupted a lot this year and that would put more pressure than ever on NCEA assessments next term, Watson says.

"The big challenge is with NCEA. Deadlines for assessment and preparation for external exams and making sure our students get the best possible academic outcomes. So that puts a lot of pressure on the third term every year, and this year in particular with the disruptions we've had in the first six months," he says.

-RNZ/John Gerritsen.