PERRIS, Calif. — The private school had a welcoming name. The principal was scientifically minded. But the Sandcastle Day School was a nightmare for the six students enrolled there.

David A. Turpin created the school inside his nondescript stucco home southeast of Los Angeles. But the only ones enrolled there were the six of his 13 children who were school age. And what took place inside was not teaching but torture, the authorities said, after they raided the house over the weekend and found a horrifying scene of emaciated children chained to furniture. The putrid smell overwhelmed them.

By creating such a school of horrors, Mr. Turpin had kept the authorities at bay. His children were never seen by teachers or counselors. Their absences never raised suspicions. On Tuesday, state and local officials were on the defensive as they tried to explain how such things could have occurred in a private school the state had sanctioned.

Mr. Turpin, 56, and his wife, Louise A. Turpin, 49, were arrested on nine counts of torture and child endangerment after one of their daughters escaped from the home out a window before dawn and called the police on a deactivated cellphone that only allowed her to dial 911. The girl, 17, showed the police photos to corroborate her story. Once the authorities entered the disheveled home, they found the Turpins’ 12 other children, ages 2 to 29. They were so malnourished that the older ones looked years younger.