It was the regular tornado drill, the one Alexander Ghassimi and other children in Moore, Okla., learn in school: Get to an interior hallway, get down, cover up. Then a teacher who had been watching the progress of Monday’s storm outside Plaza Towers Elementary School came tearing down the hall, yelling to move as many children as possible into the girls’ bathroom, and 11-year-old Alexander knew this was no ordinary tornado.

“We were in the hallway doing our procedure,” Alexander said by telephone from an EconoLodge in nearby Norman, where he was staying Tuesday with his family. “ ‘Get down. Put your hands over your head.’ ”

Perhaps 70 or 80 children jammed into the bathroom, he said. Some were standing. Some were sitting on the floor. His twin sister, Alexia, was huddled under a sink on the other side of the restroom. Some teachers were standing. When the tornado hit, they threw themselves on top of the children, he said.

“We thought we heard hail coming, then we realized it was debris,” he said. “Then we looked up and the whole ceiling was gone.”

Pressed up against a stall divider, Alexander watched the boiling storm pass overhead. “It’s kind of funny how it looked,” he said. “It almost looked like ‘The Wizard of Oz,’ just a bunch of papers and books above us.”

The roof was gone; mud and debris were raining in. Some of the children were calm, others came unglued, he said. “Everybody was just screaming, ‘Is everyone okay? Is everyone okay?’ I was almost on the opposite end of my sister, so I was trying to get to my sister. They were crying, screaming. A lot of people were just crying their butts off.”

All the fourth-, fifth- and sixth-graders in that restroom, and hundreds of other children at the school, survived one of the most powerful tornadoes in recent years, a 1.3-mile-wide monster that reached EF-5, the highest ranking on the scale that measures tornado strength. But seven children perished when the swirling winds obliterated the school, according to the state medical examiner’s office. Moore Mayor Glenn Lewis said he was told that the children died when a wall collapsed on them.

But it is becoming clear that after the decision was made to shelter the children at the school as the storm approached, teachers and staff members went to great lengths to shield them from the tornado.

The children pressed against walls in hallways or, like Alexander, crowded into at least one bathroom. The school had no safety room.

“They actually walked out. They were fine,” said Roya Partin, Alexander’s mother. “I know — it’s amazing. If you look at the school, just imagine a box of matches thrown on the floor. That’s what the whole school looks like, and everything around it.

“If you don’t believe in God before something like that, you sure do now.”

Partin was huddled at home in this suburb in a tornado-prone swath of Oklahoma, less than a mile from the school. She, her husband and two other children — ages 6 and 3 — moved to the interior of the home, blankets and pillows pulled over their heads. Their home was destroyed, but the family escaped unscathed.

Partin credited the school’s bathroom fixtures with protecting the children there. “The walls were all gone. Everything flew off,” she said. “Basically the stalls were still there. The toilet stalls, and basically that’s all that kept them from being beat up by debris.”

Partin said her children were scheduled to get out of school at 3:37 p.m. Monday, three days before the end of the academic year. “The tornado hit at 3:34 or 3:35,” she said. At 2:45, an automated phone message went out to parents: The children would be sheltered in place.

Amy and Cody Shipman, parents of a first-grader, 7-year-old Kenzi, were on the phone about that time, urgently trying to decide where their daughter would be safest. Amy, at work in Oklahoma City, pushed Cody to leave Kenzi at Plaza Towers. Cody wasn’t sure.

“We had decided to leave her there, but the storm had gotten so big that the newscasters said that if you were aboveground, you need to either run” or get underground, Amy Shipman said by cellphone from her car Tuesday as she drove to rent a storage unit for what is left of her family’s belongings.

The family lived three doors down from the school, about a city block. There is a small creek between the house and school, but no through street for a car. Cody Shipman took off on foot.

“He just ran in and started screaming her teacher’s name, and they pointed him in the direction” where Kenzi’s first-grade class was huddled against a wall.

Cody is an oil field worker in New Mexico — two weeks on, two weeks off. He was home because he happened to be off, Amy Shipman said.

He grabbed his daughter and sprinted toward the family’s home, where neighbors were opening their storm shelter. About 20 people crowded in just before the tornado hit, collapsing the school wall where Kenzi was a few minutes earlier.

“I believe she would have been on the west wall of the school,” Amy Shipman said. “That was the first side of the school that was hit.”

“They got in [the neighbor’s shelter] and held the door down,” she said. “Just rode it out.”

The Shipmans’ home was destroyed. “Our home is unlivable,” she said, “but if you compare it to the ones across the street,” it fared better. “We still have some walls, some roof.”

“Portions of our walls are missing,” she added. “Brick peeled. The garage door is in the kitchen.” Much of what they own is covered in mud.

“We may be able to salvage things,” she said, “but other people won’t have that luxury.”

Roya and Ernest Partin emerged to the almost complete devastation of their neighborhood. Their two cars were totaled, so they set off on foot to find Alexander and Alexia.

“It was like a mass exodus,” Roya Partin said. “There were people. There were cars. People were yelling at us: ‘You can’t go get down there!’ ” Someone stopped and picked them up when they said they were trying to find their children.

“It took 30 minutes to go less than a mile,” Partin said. “Everywhere was blocked off” by debris and emergency vehicles. “People were bleeding on gurneys. You saw IVs hanging and people pushing them. It looked like a nightmare, like a movie.”

“I couldn’t tell where we were at,” she said. “There was no semblance of what we knew. I said, ‘Where’s the school? Where’s the school?’ And I was freaking out, and I looked at my husband and he was crying.”

Eventually they learned that an adult had brought their children to what was left of the family’s home, where the six were reunited. Ernest Partin’s employer, Sam’s Club, has put them up in the motel for a week, but Roya Partin is unsure what they will do next.

“I don’t even know if I want to go back to Moore,” she said. “That was just too much, especially with the little one.”

Alice Crites and Jennifer Jenkins contributed to this report.