Parents will decide whether their children need to return to school next week, Prime Minister Jacinda Ardern says.

The Cabinet decision to move to alert level 3 next Monday means that schools will reopen for a teacher-only day on Tuesday April 28 and will be open for students the next day, April 29.

But Ardern reiterated that the Government "encourages" parents to keep their children at home if possible.

"We are not expecting large numbers to be in attendance," she said.