The debates over vaccinations are often cast as arguments over the integrity of science. But they can just as easily be understood as conversations about power, writes Eula Biss, a senior lecturer at Northwestern University, in her book, On Immunity: An Inoculation. As it stands, all 50 states require specific vaccines for school-aged children, although each grants exemptions for students unable to be vaccinated for medical reasons. The power struggle—pitting parents against parents—arises in the 19 states that allow families to opt out of vaccination requirements by claiming a "philosophical exemption," whether based on personal, moral, or religious beliefs.

Last month, however, one private Montessori school in Traverse City, Michigan—The Children’s House, which serves infants through children in the eighth grade—changed the power dynamic. As one parent there described it, the school wrested control from a vocal minority of people in their community who don’t believe in vaccinating their children and gave the majority who do their voice back. By revising its admissions policy and refusing to accept new students whose parents opt them out for personal beliefs, The Children’s House illustrates how schools are becoming ground zero for the anti-vaccine dispute. It also serves as an example of how educators—not state legislators or health officials—may be the ones who ultimately resolve the public controversy over immunization requirements.

Several weeks after the school year started last fall, and months before the recent measles outbreak, Jill Vollbrecht, an endocrinologist and Children’s House parent of three children ages 4 through 9, read a disturbing report by a local news outlet, the Traverse Ticker. She discovered that between 2008 and 2014, waiver rates—the percentage of those declining vaccinations for both medical and personal reasons—had climbed from 6 percent to 11 percent in Grand Traverse County, which encompasses the school. Moreover, it was now as high as 19 percent in nearby Leelanau County. Even more alarming to her at the time, Michigan health records showed that waiver rates had spiked among local Montessori students compared with other public and private schools within the state. The report showed that nearly a fourth—23 percent—of families at The Children’s House were opting their kids out of vaccinations. "I’m not a family practitioner or an infectious disease specialist, but these numbers set off alarm bells for me," Vollbrecht said. "All physicians have the common goal of wanting to keep our kids and our communities safe, and we have a core understanding about science and herd immunity."

Vaccines only work if enough people in a community are vaccinated—what Vollbrecht referred to as herd immunity. As Biss writes in her book, vaccines are a kind of immunity banking, something an individual may need at a future point in their life: "When enough people are vaccinated, viruses have trouble moving from host to host and cease to spread, sparing both the unvaccinated and those in whom the vaccination has not produced immunity." Researchers have found that, for vaccines to work, 92 percent or more of a population must be immunized against the disease. For highly contagious viruses, it takes 95 percent to protect the entire community.

By either measure, both Grand Traverse County and The Children’s House appeared to have dangerously high exemption rates. At the school in particular, the risk of losing herd immunity was disconcerting because it enrolls babies as young as 3 months old—infants who still aren’t fully vaccinated and rely on the rest of the school to shield them from outbreaks that can be life threatening for young children. In fact, earlier this week, the Los Angeles Times reported that a months-old baby who was too young for vaccinations contracted measles at daycare, forcing the subsequent quarantine of 14 infants enrolled at the same center, which is located on Santa Monica High School’s campus.

So, after seeing the waiver rates this fall, Vollbrecht and a fellow parent and physician, Daniel Flewelling (whose 2-year-old also attends The Children’s House), contacted the school’s head to determine why so many parents were opting out of vaccines and how they could change the admissions policy as quickly as possible. In their view, the state certainly wasn’t helping. According to an MLive analysis of health data, Michigan had made it so easy to sign a waiver that, last December, nearly 45 percent of its residents lived in counties that were at risk of disease outbreaks. And the threat to Traverse City’s children wasn’t merely theoretical. Just a month earlier, the county health department confirmed 22 cases of pertussis, what’s commonly called whooping cough, and even had to temporarily close one of its K-12 charter schools, Grand Traverse Academy. In response, Michigan recently bolstered its policy for daycare centers and licensed schools, requiring parents who refuse vaccinations because of personal beliefs to have their waivers certified by the local health department. In other words, the updated policy means that exemptions are now more than a "check-the-box" formality.

But for Michelle Shane, who heads The Children’s House, Michigan didn’t go far enough. The Ticker article, coupled with Vollbrecht and Flewelling’s concern, prompted Shane to analyze the school’s data on vaccine-exempted children more carefully. She discovered that the 23-percent figure included parents who were signing waivers simply for convenience. For example, some families had simply postponed their back-to-school doctors’ appointments. Shane reckoned these parents were signing the waivers not because they intended to avoid getting their kids’ immunized but because, at least under her watch, the school had always emphasized compliance with state reporting requirements; they didn’t have much of a choice other than to file for exemptions. After removing those families from the list of kids who had waivers, Shane discovered that only 15 percent of the student body was unvaccinated because of their parents’ personal beliefs.

Not all families have supported the school’s change in admissions policy.

"There were people who were really upset when we announced our decision," said Shane, who ultimately decided that existing unvaccinated students would be grandfathered under the new policy. "But let’s focus on the 85 percent of parents who do vaccinate and those who were extraordinarily pleased with the outcome."

M., a Children’s House parent who opposes the policy and wished to remain anonymous, believes the school’s decision and process ran counter to the Montessori philosophy. "I believe the school is about embracing options, considering diversity and looking at culture," she said. "Montessori encourages children to ask questions, to seek out information, as the school continues to do this with other educational programs." Yet, she explained (and Shane acknowledged), there was no open forum for parents to discuss the policy before it was enacted, nor were parents of unvaccinated children invited to share their opinions or suggestions. "Comfort is relative, but for the most part, we still feel respected," she said, "And I want my kids to have a Montessori education and options are limited in Traverse City."

The idea behind Montessori schools is that they’re meant to mirror "the real world," where individuals work and socialize with people of all ages. Mixed-age classrooms are one of the hallmarks of the Montessori teaching method, which means that infants, kindergarteners, and adolescents come into contact throughout the school day. Vollbrecht described how babies and toddlers attend student performances and gather in the gym for school-wide assemblies, adding that she frequently finds her own 6-year-old playing with sixth graders when she picks her up after school.  Shane, meanwhile, explained that preschoolers are encouraged to eat lunch with the older students. In this case, like "the real world," students at The Children’s House are exposed to a community with a range of physical conditions, such as infants who are unable to be vaccinated.

While drafting its new policy, The Children’s House consulted Frederick Bimber, an attorney in the area. He explained that while private schools typically have more leeway in implementing regulations, there is considerable legal precedent for states to set immunization requirements for public schools, too. In 1905, in a case that’s still cited to this day, Jacobson v. Massachusetts, the U.S. Supreme Court held that states have the legal authority to mandate vaccinations for all residents.  And in 1922, the court reinforced the government’s ability to require vaccinations as a condition of school attendance. By 1970, most states had enacted policies allowing parents to not vaccinate their kids on religious grounds, according to Leslie Meltzer Henry, a law professor at the University of Maryland and faculty member at the Johns Hopkins Berman Institute of Bioethics. But to qualify for these exemptions, families had to demonstrate that vaccinations violate the teachings of a recognized religion to which they belonged. In some cases, state health boards asked parents to get notes from a clergyman. And over the years, a number of courts found these policies unconstitutional under the First Amendment because they required the government to determine whether a person’s religious beliefs are valid—an act that entangles the state with religion. In an effort to avoid these problems, Henry said, 19 states either replaced or expanded their existing religious exemptions with broader personal-belief ones, which turned out to be a double-edged sword.

On the one hand, these personal exemptions are a sign of progress in that they treat religion as only one of a variety of individual belief systems that influence people’s medical choices, for themselves and their children. On the other hand, as Henry explained, strong evidence reveals the grim public-health reality of these exemptions: States that allow people to opt-out for personal beliefs have lower childhood-vaccination rates and significantly higher incidences of infectious diseases compared with states that don’t. According to a 2006 report in the Journal of the American Medical Association, Vermont, for example, has a relatively liberal personal-exemption policy and experienced a higher incidence of pertussis between 1986 and 2004. Nebraska, in contrast, didn’t allow personal exemptions and had a significantly lower number of Pertussis cases in the same time frame.

Further complicating matters, case law allows schools to exclude unvaccinated students, even those with religious exemptions, during periods of infectious disease outbreak, according to Bimber. But school administrators don’t always agree with that premise, as was recently the case one San Francisco-area school district. The issue arose when Carl Krawitt, who lives in Marin County—a community with one of the highest personal exemption rates in the state—emailed the district’s superintendent late last month amid the ongoing measles scare requesting that students who lack vaccinations for non-medical reasons be barred from his son’s elementary school. Krawitt’s 6-year-old son, Rhett, has been fighting leukemia for the past four and a half years. While the little boy’s cancer is in remission, his immune system is still too compromised for vaccinations—a particularly difficult circumstance given that around 7 percent of the families with students at his Bay Area elementary school reportedly opt their kids out of immunizations. Matt Willis, the county health officer, denied Krawitt’s request, citing the balance between controlling communicable disease and maintaining "everybody’s right to freedom." Although Krawitt was unsuccessful in his endeavor, his decision to appeal the policy through the education system exemplifies the degree to which schools are emerging as key players in the vaccine debate—and how they, unlike statutory reform, have the opportunity to take swift, decisive action when there is an outbreak. It took The Children’s House, for example, only four months to develop a new admissions policy in the face of surprising statistics. Getting rid of personal-exemption policies, state by state, could take years, if not decades. (Just this week, California lawmakers introduced a bill that would tighten up its exemption policy, making it more difficult for parents to opt their kids out of vaccinations for personal reasons.)

In addition to parents, other stakeholders in the education world are now entering the vaccine debate. This week, the American Federation of Teachers urged parents to vaccinate themselves and their children. But the teachers’ federation acknowledges the challenges educators face. Patricia Forrai-Gunter, a school nurse who serves on the board of the Cleveland Teachers Union, was cited in the national union’s press release as saying, "Our hands are tied … What we need more than anything else is the support from state and local leaders to make sure families are educated about the importance of immunizations for their children, our school systems and communities nationwide."

And what about a school’s legal responsibility to its students? Dorit Reiss, professor at Hastings School of Law, has written extensively about the potential legal ramification of not vaccinating a child and giving parents of an infected child the right to sue. But Reiss believes a court might have trouble finding a school negligent for allowing unvaccinated children to attend, absent an outbreak. However, she clarified, during a health threat, such as the current measles one, schools do have the authority to bar unvaccinated students. And they could, she said, potentially be held legally accountable, by a parent or a teacher, for not protecting their community.

In her book, Biss writes about how her father, a doctor, explained immunization to her: "Vaccination works by enlisting a majority in protection of a minority." As The Children’s House ambitious new policy shows, schools may ultimately decide, one by one, whose voice is most powerful: the majority of families who vaccinate or the minority who don’t.