The boy and his family are in isolation and are being tested today. As a result, Watkins contacted the Medical Officer of Health and was given the advice to operate the school as normal as nobody in the pupil's family was showing signs of illness and the chances were "relatively slight" the family had the virus.
Watkins said as nobody else in the class came into direct contact with the grandmother, there was no need for the children to self-isolate, or for the school to close.
Speaking to the Rotorua Daily Post, Watkins said he had "absolutely no problem" with parents coming into the school and picking up their children if they preferred.
"Since the information has been out I have had streams of parents coming into school and my message is, if that's what you want to do, I have absolutely no problem with that."
Watkins said the school attendance was down at least a quarter and he believed it was the same for many schools in the Rotorua district.
His concern was the ability to establish an online learning platform while teachers were also expected to be in the classroom and he did not want to see children missing out on education.
Today the Government announced schools and other non-essential services across New Zealand would be closed for at least the next four weeks as the country is put in lockdown to try to stop the spread of coronavirus.
All schools would close from tomorrow except those attended by the children of people working in essential services, so they wouldn't have to make emergency childcare arrangements.
All schools will close entirely from midnight Wednesday.
In the Facebook post, Watkins advised parents to keep children at home if they were unwell or had a compromised immune system.
"The Medical Officer of Health is following this case and will provide us with further advice once he has the test results back for this family.
"We are entering uncharted waters and completely new ground with this virus.
"Wherever possible we would want all of our students here and to continue with normal life at school."
The school has postponed the Year 6 Marae noho, Year 5 camp and the Year 1 picnic until later in the year, while the Year 4 sleepover has been cancelled.
"We will not have team gatherings, kapa haka, or assemblies, as these are large gatherings of over 100 students, until further notice," he said.
Students were eating morning tea and lunch in their rooms rather than as a large group on the school field.
Watkins said now more than ever, communication between home and school was really important.
He asked school whānau to keep him informed of any developments in their family, and he would do the same.
"We are in regular contact with the Ministry of Education about how best to handle this pandemic.
"We are receiving updates at least twice each day, which provide up-to-the-minute advice and guidance on what we need to be doing to keep our students safe. As information comes to hand, we will keep you updated."
He said the staff were regularly reminding students about hand washing, nose-blowing, coughing into their arm or elbow, and maintaining their own personal hygiene.