It comes as some school districts reopen classrooms for the new school year, CBS2's Meg Baker reported Monday.
With their backpacks and masks on, students in Chatham headed back to school.
Middle schoolers in Summit left with smiles on their faces.
"It was way better than being virtual. I could see my friends and teachers," said 7th grader Eilon Behiri.
"I'm looking forward to learning new things in my new classes," said 6th grader Anna Harrison.
"This pandemic has just been outrageous for these poor kids. So, I think she was very happy to get to school. I hope she maintains that attitude all year," said father Rich Boyd.
Gov. Phil Murphy had a message Monday for districts pushing back on the state's mask mandate in schools.
"Our in-school masking policy is not a polite suggestion. We do not and will not take lightly to any district or any school that tries to finagle their way out of their responsibility for protecting public heath," Murphy said.
Dr. Meg Fisher, a pediatric infectious disease specialist and advisor to the Commissioner of Health, said the Delta variant is spreading quickly among younger people, but serious illness is rare.
"We actually have not seen an increase in severity or hospitalizations of children," Dr. Fisher said.
Many children have no symptoms at all.
"Some of them have a mild cold. And then, children, particularly those who have underlying problems, can get more severe illness with fever, aches and pains," Fisher said.
Health officials say some of the best protections are masking, social distancing and staying home when sick.
"If their child is 12 or older, get them immunized. We know that's the best protection," said Fisher.
"What are the long term effects? Do we even know?" Baker asked.
"This disease has been around for 15 months, so of course we don't know what's going to happen in 20 years from now. But we have pretty good evidence that for the vast majority of children who are infected, there are not long term effects. Are there exceptions to the rules? Of course," said Fisher.
Parents told Baker they support masking to protect their younger, unvaccinated children and the community. Kids said masks have become a fashion statement.
CBS2's Meg Baker contributed to this report.
for more features.