An Auckland primary school has been forced to delay the start of term until next week, due to all teaching staff awaiting Covid test results.

Thousands of children around the country are expected to return the classroom this week for the beginning of the school year.

In a letter sent to the school community yesterday, the board of trustees of Reremoana School, in Wattle Downs Auckland, said all teaching staff were now isolating.

"All of our teaching staff have been deemed close contacts to a positive Covid-19 case following a staff training day on Thursday," read the letter.

"They are all getting tested and awaiting results and further instructions, but will all be required to self isolate until at least next Sunday."

Principal Julie Cowan said 27 of the school's teaching staff had attended a professional development day at another school last Thursday.

"All attendees wore masks, doors and windows were open and all requirements at 'Red' were followed," she said.

Taking advice from Healthline and the Ministry of Education, all staff were being tested and were now isolating.

"This has required an adjustment of the start date to ensure we have our teaching staff available to give our students the best start to the school year possible after so much disruption last year.

"We know this is frustrating and disappointing to our community and students and we are all looking forward to starting the school year."

Cowan said she suspected isolation requirements would be something schools continued to grapple with over the coming weeks and months, as Omicron spread throughout the community.

The school advised the office would remain open this week, as the office staff had not been exposed to Covid-19.

With schools returning amid an Omicron outbreak, the Government has made changes with how schools deal with Covid, including increasing isolation time for confirmed cases, scrapping the casual plus contact, and treating vaccinated and non-vaccinated confirmed cases the same.

It has also introduced mandated boosters for eligible teachers by March 1. They need to have received two Covid-19 vaccinations as well as a booster dose by this date, providing it has been at least 183 days since they received their second vaccination.