Tens of thousands of students on Long Island headed back to school Thursday for their first day of classes amid concerns about mask requirements and safety measures meant to keep them safe.

Infectious disease expert Dr. Bruce Farber says the highly contagious delta variant makes it even more critical for students and schools to take safety precautions.

"It's all the more reason why it's important particular for the large number of unvaccinated children who are under the age of 12 to be wearing masks in school," he says, "and I fully support the need for masks for children in school to decrease the risk."

Farber says now is not the time to ease mitigation practices, including masking and social distancing in schools. He says failure to do so could lead to an outcome many want to avoid.

"Schools are not going to be allowed to remain open, which is what we desperately want to avoid," Farber says.

School officials in the Plainview-Old Bethpage school district say they have mitigation measures in place, including masking and social distancing. News 12 is told unvaccinated staff members are also required to undergo COVID-19 testing once a week.

The surge in the delta variant has also intensified debate among parents over the mask mandate. Ben Daidone, of Massapequa, says he doesn't like the idea of masks on his kids but won't fight the state mandate.

"I'm not really too fond of it, but if that's what they feel is going to keep the kids safe then that's what they'll have to do," he says.

Others say as long as COVID-19 is a threat, students need to mask up.

"The science is pretty clear about how this is transmitted and the consequences of it being transmitted, so, you know, I will follow the science," says Jenny Isaacs, of Massapequa.

The last districts that will have children back in school Friday are Floral Park-Bellerose and William Floyd.