The parents of 13 children are accused of holding them captive in this Perris, Calif., home. Authorities said an emaciated teenager led deputies to the home where her 12 brothers and sisters were locked up in filthy conditions, with some malnourished and chained to beds. (Alex Gallardo/AP)

Shortly after news broke that 13 home-schooled children had allegedly been held captive in their filthy California home, some chained to furniture, Rachel Coleman got a message from a colleague: “Why is this case the one making international news?”

The accusation against the Turpins — with children ages 2 to 29, reportedly malnourished and living in conditions authorities called “horrific” — isn’t the first allegation of abuse made against parents who claim to be home-schooling their children.

The story of the Turpin family — with siblings, ages 2 to 29, reportedly malnourished and living in conditions authorities called “horrific” — is hardly the first involving the abuse of children kept at home by parents who claim to be home schooling them. And like those earlier episodes, it highlights how parents home schooling their children operate amid scant state regulation, said Coleman, founder of the national nonprofit Coalition for Responsible Home Education.

There was the case of a home-schooled 7-year-old Kansas boy who was tortured for years at the hands of his father and stepmother before he was murdered and his body dumped in the family pig sty, where authorities found his emaciated remains in late 2015.

In November 2017, a 6-year-old weighing 17 pounds was brought to an Illinois hospital, dead, by his father, who was home schooling his children with his wife, police said.

And in Ohio, authorities in 2005 discovered 11 home-schooled children with special needs, ages 1 to 14, all of them foster children or adopted, and kept in cages in their home.

“We’ve seen so many cases that for us, the Turpin case is not that abnormal,” Coleman said. “It fits this pattern we’ve been tracking for a long time.”

To be sure, she said, the vast majority of home-schooled children have parents who create a warm environment at home and provide a fine education. She was happily home schooled, as were other staff members of her organization. The California case, she said, is “not the norm.”

But, she said, the lack of regulation and enforcement by states allows home-schooling parents who abuse their children to hide them. While children who attend regular schools are abused too, research shows that home schoolers account for a disproportionate number of abused children.

A 2014 study by University of Wisconsin pediatrician Barbara Knox and colleagues found that in 38 cases of severe child abuse, 47 percent of parents had never enrolled their children in school or pulled their youngsters out when abuse was suspected and told authorities they were home schooling.

The National Center for Education Statistics reports that 3.3 percent of U.S. students, ages 5 to 17, or about 1.7 million, were home schooled in 2016. A survey of parents found that the most important reasons for home schooling were concern about school environments (34 percent), dissatisfaction with academic instruction (17 percent), and a desire to provide religious instruction (16 percent.)

In the case of Adrian Jones, the Kansas boy whose body was dumped with pigs, a prosecutor last year called for stronger regulations of home schools — but the legislature didn’t follow through. In fact, Coleman said, no state has strong protections and enforcement for home-schooled children.

Only one state, Arkansas, bars home schooling when a registered sex offender lives in the home, but Coleman said authorities in that state don’t check. Only Pennsylvania prohibits home schooling when any adult in the home has been convicted in the last five years of a crime that would prohibit teaching in a public school. No other states have requirements of that sort.

New York and Pennsylvania have the most requirements for home-schooling parents, but neither makes sure families have not been involved with child protection authorities because of past neglect. In California, where the Turpin family was discovered, there is no home-schooling law and parents can set up “private” schools at home with no state oversight.  Nine other states allow home schoolers to operate as private schools. (You can see data on this here.)

Coleman’s organization is pushing for states to adopt two strategies that, she said, responsible home schoolers already abide by.

She said parents who home school should be required to take their children to a doctor annually or on some other regular basis, and they should be required to allow a third-party — approved by a school system — to regularly assess student work through a standardized test or a portfolio reviewed with the child present. An independent third party would have, for example, seen the translucent skin of a home-schooled boy who had been kept in his bedroom, with his windows taped, for four years by his parents in Georgia, and then put on a bus to Los Angeles, where police found him in 2012, she said.

Some home-schooling groups fight proposed regulations, including the Virginia-based Home School Legal Defense Association.

“What happened in California is horrific,” said Mike Smith, spokesman for the home school association. “But there will be people like this, and regulation doesn’t stop them generally. To then put regulation on all the other [home-schooling] families who do an outstanding job, I don’t think it’s fair to them, and I don’t think it accomplishes what it is meant to accomplish.”

He said adults haven’t been able to prevent the abuse of children who attend public schools. And he cited a 2016 federal report that found previous abuse in a family was the top risk factor for future abuse. The report said government authorities frequently fail to act on information pointing to abuse.

Coleman said that underscores her point that states don’t do enough to ensure that abused children aren’t being home schooled and that home-schooled kids aren’t abused.

“We’re not saying that we can catch everyone,” Coleman said. “There is no perfect system. But you don’t let the perfect be the enemy of the good.”