PORTLAND (AP) — Schools featuring out-of-the-mainstream curricula are attracting clusters of parents skeptical of conventional medicine — and so large numbers of the pupils in those schools aren’t getting common childhood vaccines.

The Oregonian newspaper reported it found 23 public and private schools in Oregon with unusual clusters of students with immunization waivers for religious reasons as it examined data released after a public records request.

Oregon requires vaccines for 11 diseases but allows parents a religious exemption, which can be based on “any system of beliefs.” If there’s an outbreak at school, state law requires that parents with waivers keep the children home until the threat passes.

Statewide, 3.9 percent of kindergartners and 2.6 percent of seventh-graders had such a waiver last year. The state annually reports to the CDC data from those two grades, as well as day care centers and preschools.

But, The Oregonian reported, many schools have larger proportions of unvaccinated students — ranging in public schools up to one out of three kindergartners at Ashland’s Walker Elementary and Portland’s Sunnyside Environmental K-8 and in private schools up to two out of three kindergartners in Portland’s Cedarwood Waldorf School and Milwaukie’s Portland Waldorf.

Public health officials said they’re concerned about the concentrations.

“We have a number of medically fragile children in our school system,” said Kimberly Bartholomew, a Beaverton school nurse and member of the Oregon Partnership to Immunize Children, a state coalition. “These children can only be protected if their classmates are immune.”

Fully vaccinated children should be protected from an outbreak, even if many of their classmates are unvaccinated. But in some vaccinated children, a vaccine doesn’t take, meaning they’re not protected against that disease and also could expose family memebers with weak immune systems.

Jody and Henrik Bothe of southeast Portland, themselves fully immunized, have so far skipped all vaccinations for their two children.

The children attend Portland Waldorf School, which emphasizes the arts, fantasy and play and postpones teaching children to read.

The Bothes say they are deeply skeptical of the motives of profit-making drug companies that manufacture vaccines and confident that humans can successfully recover from diseases they encounter in nature. The CDC’s recommended vaccination schedule, they say, bombards immature immune systems with a host of antigens.

“I basically think it’s a big money machine, and that’s why they’re pushing it so early,” Henrik Bothe said.

Jody Bothe said it’s important for children to get sick. “Great, get the chickenpox. Great, get the measles. They get strength from sickness.”

Natural immunity can come at a hefty cost, says Bartholomew, the school nurse.

“We must keep in mind that after natural infection from a vaccine-preventable disease,” she says, “there is the potential for a variety of serious complications such as blindness, pneumonia, mental retardation, brain damage, seizures and death.”