Other parents waited even longer, as they drove from one emergency shelter to another in search of their children.
At St. Andrews United Methodist Church, 15-year-old Caitlin Ulrey waited about seven hours before her parents found her. Her high school had not been hit by the tornado. But her nerves were frayed.
"I was starting to panic and shake and have an anxiety attack," Caitlin said.
At Plaza Towers, several students were pulled alive from under a collapsed wall and other heaps of mangled debris. Rescue workers passed the survivors down a human chain of parents and neighborhood volunteers. Parents carried dazed and terrified children in their arms to a triage center in the parking lot.
Hundreds of Oklahoma schools have reinforced tornado shelters, but not the two that were hit on Monday.
Albert Ashwood, director of the Oklahoma Department of Emergency Management, said it is up to each jurisdiction to set priorities for which schools get funding for safe rooms. But he said a shelter would not necessarily have saved more lives at Plaza Towers. The tornado was an EF5 twister, the most powerful type, with winds of at least 200 mph.
"When you talk about any kind of safety measures ... it's a mitigating measure, it's not an absolute," Ashwood said. "There's not a guarantee that everyone will be totally safe."
Moore School Superintendent Susan Pierce said teachers and administrators put their well-rehearsed crisis plan into action as the tornado approached. But she suggested there are limits to what people can do in the face of such a powerful storm.
"Safety is our main priority," Pierce said. "We monitored the weather throughout the day and when it was time to shelter, we did just that."