The North Carolina School with a large community against vaccination is at the heart of the country's largest chicken pox outbreak for decades, officials say.
On Friday, 36 students were diagnosed at the Asheville Waldorf School, the newspaper Citizen reported.
The school is one of the highest rates of state religious exemption, allowing students to skip vaccination.
US health officials said vaccinations were far safer than chickenpox.
"This is the main cause of chickenpox outbreaks of health officials aware that the vaccine has been made available," the North Carolina Health Ministry spokesman told the BBC in an e-mail.
Of the 152 students at the Waldorf School, 110 did not receive the vaccine for the varicella virus, the most commonly known as chickenpox.
And 67.9% of school kindergartens received exemptions from religious guards in the 2017-2018 school year, according to state data.
The elementary school had full cooperation with local health officials and was in compliance with all laws in North Carolina, a school spokesman told the BBC.
"We find that our parents are highly motivated to choose exactly what they want for their children, and we, as a school, do not discriminate based on the child's medical history or medical condition."
The Buncombe district, home to the city of Asheville, with a population of over 250,000, has the highest rate of religious-based exemptions in the country.
Local health officials closely monitor the situation, according to the district health department.
"We want to be clear: vaccines are the best defense against chickenpox," said Dr. Jennifer Mulandora, director of regional medicine.
"When we see a large number of children and adults not threatened, we know that a disease like chicken pox can easily spread throughout the community – to our playgrounds, to the grocery stores and to the sports teams."
North Carolina law requires certain vaccinations, including chicken pox, measles and mumps to kindergartens, but the state allows for medical and religious exemption.
Most religions do not forbid vaccination, but in recent years some parents in the United States have been fearful of negative responses to vaccines.
While some bad reactions, like allergies, and possible vaccinations, the medical community has debunk the vast majority of these fears, and groups including the World Health Organization and the American Academy of Pediatrics encourage vaccination.
What is chickenpox?
Chickenpox is a viral infection that causes bloating-like rash, itching and fever. In severe cases, it can lead to complications like inflammation of the brain, pneumonia and death.
The virus spreads through contact or sneezing cough, although it is not contagious like measles, which can be spread without contact.