The Californian home where David and Louise Turpin allegedly put 13 children through torture was also listed as a private school, but it was not inspected by education officials.
David Turpin had named the school the Sandcastle Day School and it had six pupils enrolled in the last academic year, according to The Guardian.
Authorities don't believe there were any other children attending apart from the Turpins.
There is no regulation agency over private schools in the state, but they do have to provide information about students, staff and administrators.
Despite this, private schools can be inspected by either a local fire marshal or the state every year. It is not clear whether this type of inspection ever took place.
Many are now questioning how the school was never investigated and how the alleged abuse was kept secret.
Authorities claim they were alerted to the matter when a 17-year-old girl escaped the home through a window and called the emergency services.
It is claimed she then informed police of her 12 siblings, some of whom were allegedly chained to furniture and malnourished. The 13 are aged between two and 29 years old.
Riverside county sheriff’s department has praised the "courage of the young girl who escaped from that residence to bring attention so they could get the help they so needed.”
Captain Greg Fellows described conditions at the home as "horrific" but also said Louise Turpin did not seem to understand why police were visiting her home.
It is not yet clear why the family were allegedly living in such conditions.
The parents may face both charges of torture and child endangerment and are being held in custody with bail set at $9 million.