ABC NEWS -- As the terrified tornado-whipped students of Briarwood Elementary School in Moore, Okla., cowered on their hands and knees with backpacks over their heads, tearfully pleading for their parents, they asked their teacher, "Is this really happening?"
Sheri Bittle, a first-grade teacher at Briarwood, today recounted the horror of Monday's twister that she said sounded like a train that kept barreling by as it ravaged her school.
"You could just feel the pressure just building like you were in an airplane, just the pressurization of the cabin and your ears popping and the debris starts flying and the roof falling in," Bittle told ABC News. "And everything in your classroom falling in on you."
FULL COVERAGE: Oklahoma Tornado
The tornado tore a 12-mile path of destruction that killed 24 people, including nine children, and destroyed Plaza Towers Elementary School and Briarwood Elementary School in Moore. For many families, Monday ended in tears of joy after families were reunited. Others were left to wait, hoping for good news while fearing the worst.
"I actually saw the tornado coming straight toward us," Briarwood first-grade teacher Cindy Lowe told ABC News. "I knew there was no turning back then. It was coming. It wasn't something that I was watching on TV. This was really going to happen."
Teachers followed procedure, Bittle said, moving students to interior walls and the innermost area of the school. The children got down on their hands and knees, putting their hands over their heads.
"They were covering their heads with their backpacks," Bittle said. "There was so much debris falling. A roof beam fell on me and another teacher."
Bittle, who escaped major injury, lay on top of her children as the building collapsed around them and said all the teachers would have done the same. A teacher in the next room had a table leg impale her own leg.
"I was praying," Bittle said. "I yelled it over and over for the Lord to just cover us and save us and to keep us safe. And He did. My entire class was safe and well and got delivered to their parents. The teachers at Plaza Tower didn't have that blessing."
Seven of the nine children killed in the tornado were students at Plaza Towers Elementary school, officials said.
"I can't imagine," Bittle said through tears, "not being able to give those kids back to their parents that brought them to me that morning."
Oklahoma County Commissioner Brian Maughan confirmed to ABC News affiliate KOCO-TV today that a number of children at Plaza Towers Elementary School remain unaccounted for.
"It's just a very graphic situation for even those of us who've come obviously well after the storm has passed," he said.
RELATED: Tornado Deaths Revised Down to 24
"I know there's a number of dead children from that school," Oklahoma City Police spokesman Sgt. Gary Knight said.
The walls of Plaza Towers Elementary School were "pancaked," Oklahoma Lt. Gov. Todd Lamb told ABC News.
The storm tore off Plaza Towers' roof, knocked down walls and turned the playground into a mass of twisted plastic and metal. Rescue workers passed the survivors down a human chain to the triage center in the parking lot after the tornado passed directly over the school. Briarwood Elementary School received a "direct hit" from the twister and was also destroyed, with its roof and walls blown off.