Parents are being urged to keep sick children at home while winter illnesses, including strep throat and a "particularly nasty virus" do the rounds in Rotorua.
John Paul College principal Patrick Walsh said his school had been hit hard this winter and it seemed the time it was taking for people to recover was longer than in previous years.
"Staff have been largely impacted. At one point there was eight or nine teachers away in one day. It's not something that can be helped but it certainly isn't ideal.
"Students are missing out on having their normal teachers and it does put strain on the pool of relief teachers we use.
"It also seems like staff and students are not bouncing back as quickly. This winter we have had teachers out for a week, sometimes two."
He said it was primarily strep throat and flu symptoms people were coming down with.
"We've had to encourage kids to actually stay at home if they're sick. Being crammed into small spaces these illnesses do tend to spread quickly."
Rotorua Intermediate School principal Garry de Thierry said they too had a large number of sick students and teachers.
"Most of the teachers are hanging in there as it's the last week until the school holidays but there is a lot of coughing, sore throats and colds.
"It doesn't appear to be as bad with the students as it is with the staff. That said though, there has been a lot of students off, getting them right before the school holidays."
Mr de Thierry said he had noticed staff and students were not getting better as quickly.
"Normally they would take a day or two and then be right but this seems to be a particularly nasty virus where it is taking two or three weeks to come fully right again."
Kaharoa School principal Warwick Moyle said they had recently had a lot of children away with winter illnesses.
"It is what it is, but we have been hit quite hard, I'd say there's been four or five children out with colds from each class."
A spokeswoman at Otonga Rd Primary School said "a few children" and one teacher had strep throat, but it was "nothing out of the ordinary".
Rotorua GP Dr Harry Pert said a lot more winter illnesses had been presenting in the last week or so.
"Most are viral and there is not much we can do, other than to say stay at home and drink plenty of fluids.
"If a child has a streaming nose, sore throat and a temperature, it is likely a virus, however if it's just a sore throat and temperature with no other flu symptoms, it could be strep throat and we advise parents to come in and get a throat swab."
He said it was likely people were being hit with one virus after the other.
"Most viral infections last between five and seven days. If it's taking longer to recover, it may be that they were just recovering from one when a second came along."
He said it was vital parents kept their sick children home from school.
"Unfortunately there are too many cases where daycares and schools are being used as babysitters for sick children. If your child is sick, keep them at home."