The guidance said children could go to class if they had symptoms including a mild cough, headache or runny nose but appeared well and had not had a fever or required medication to reduce a fever in the past 24 hours.
But they should stay home if they tested positive for Covid-19 or had symptoms including fever, vomiting, diarrhoea or head lice.
The guidelines on the Health New Zealand Te Whatu Ora website said children should return to class as soon as they were well enough, even if they could not manage a full day at school.
"If your child cannot manage full days to begin with, discuss a transition plan with their school," the guidance said.
"In general, a doctor's certificate or clearance should not have to be provided for your child to go back to their school after being unwell."
The revised guidelines were part of a government push to improve school attendance.
They said going to school every day was important for all school-aged children.
Associate Education Minister David Seymour said absences due to illness had risen since the start of the pandemic.
In term four last year, 5.1 percent of class time was lost to illnesses, slightly down from the same term in 2022 but higher than the figure of 3.2 percent for term four in 2019.
"School attendance is a shared responsibility, and for too long attendance has not been good enough. Covid-19 had a big impact on attendance rates, attendance culture, and what is being considered acceptable. It's time to take a more rational approach and get kids back to school," Seymour said.
"Of course, health's important, of course you've got to be responsible - but you don't keep people home under all circumstances. Sometimes you've got to make a call between health and education, and we're bringing back some balance in that regard.
"Parents know their children best and should be supported to make good decisions. For example, a child with mild hay fever might display some symptoms, but that doesn't mean it's unsafe for them to attend school."
Principals' Federation welcomes guidance
Principals' Federation president Leanne Otene said it was good to have clear guidance from health professionals.
But she indicated the guidance might not have much impact on school attendance.
She said schools might have one or two pupils who were kept home when they should really be at school, but in her experience the bigger problem was children sent to class despite being seriously ill because both parents were working and there was nobody at home to look after them.
"Sometimes we've got young people at school that are really, really unwell and shouldn't be [there] because mum or dad as their caregiver is unable to care for them," Otene said.
"We have more sick children at school than we should have and transmitting nits or scabies or even a bad flu, I mean it just goes through a classroom so quickly and then you've got staff down and you've got more children away."
Explicitly including head lice as a reason to keep a child home was helpful, she said.
"That's always contentious, having that discussion with parents about needing to take their children home because that is transferable. So having that guidance to say yes they should stay home until they've had a first round of it [treatment] is helpful for school leaders."
Deciding whether to keep children home was up to parents and the guidance would help them with that decision, Otene said.
Anxiety was included in the guidance, which suggested schools work with families to support children to attend class as much as possible.
Otene said treating anxiety was beyond the capability of school teachers and schools needed a lot more help working with children who suffered from anxiety.
