Moore, Oklahoma (CNN) -- Oklahomans will "rise again" and will have the nation behind them as they struggle to bounce back from tornadoes that tore through the state last week, officials said Sunday, a day of quiet reflection and prayer.
"As fellow Americans, we're going to be there as shelter from the storm for the people of Moore who have been impacted," said President Barack Obama. "And when we say that we've got your back, I promise you that we keep our word."
The president described himself as a messenger speaking on behalf of the entire nation as he toured storm damage Sunday. He praised local officials, first responders and school principals for their work in the wake of the storms, which killed 24 people, injured more than 375 others and damaged 12,000 residences in and around the Oklahoma City metropolitan area.
"This area's known more than its share of heartbreak, but people here pride themselves on the Oklahoma standard ... being able to work through disasters like this and come out stronger on the other side," he said.
Speaking in front of the wreckage of the destroyed Plaza Towers Elementary School in Moore, Obama called for Americans to donate to help storm relief efforts.
"It's going to take a long time for this community to rebuild, so I want to urge every American to step up," he said, suggesting donating via the American Red Cross website.
After his public remarks, Obama met with first responders at a Moore fire station.
"We got to talk to him after he saw the damage, and of course, once you see the damage, it's different," Moore Police Sgt. Jeremy Lewis told CNN affiliate KOCO. "No matter how many pictures you look at, you see it in person, it's going to to change even the president, which it did."
Obama vowed to keep helping the area rebuild, long after camera crews and reporters from around the country leave.
"He ... let us know that after all the media and everything is gone, he'll still be sending anything that we need," Lewis said, "and he'll make sure that we get the town built back up."
It's been a weekend of highs and lows for the tornado-ravaged area.
With some school buildings still in shambles, students received diplomas at a convention center on Saturday.
Funeral homes and churches were busy with services nearly a week after the devastating storm.
A public memorial and prayer service was held Sunday evening at the First Baptist Church in Moore, where tissues were laid out in the pews.
"Our spirits have been shaken this week," Oklahoma Gov. Mary Fallin said at the service.
"Our hearts have been broken, but our resolve is strong and we will rise again. In the midst of human tragedy, we've seen the best of Oklahoma come forth."
Fallin held up two items she found in the wreckage of a school -- a note from a student, and a poster with classroom rules, imploring children to always do their very best.
She welcomed a teacher and a group of students from Briarwood Elementary. The school was destroyed by the tornado, but everyone survived.
Holding flowers, the students sang "Jesus Loves Me," a song some of them were singing as the storm blasted their school.
"I think it was probably the start of healing for the community," Debby Goss, a Shawnee, Oklahoma, resident, said about the prayer service.
"I think a lot of people do pull together here, and this was a good time for them to see each other in one place that wasn't a rescue center or a disaster area -- that there was a peaceful place for them to just sit and think about the other people that are here to support them and help."
Saturday's graduation festivities were infused by reminders of the storm's tragic aftermath.
When Southmoore High's Alyson Costilla walked across the stage to get her diploma, about a dozen people in the crowd stood and held up pictures of her mother, who died in a 7-Eleven ravaged by the powerful winds.
Transforming Moore back into the city it was won't be easy. Its public schools alone suffered $45 million in damage, including the two elementary schools that were leveled. Insurance claims related to Monday's storm will likely top $2 billion, according to Kelly Collins from the Oklahoma Insurance Department.
But residents aren't doing it all alone.
Besides the presence of Federal Emergency Management Agency representatives and other public officials on the ground, they've had friends, relatives, even strangers come out to help.
Last week, Caleb Allison stared out at the mass of debris that covered the yard in front of his destroyed home.
"Who's going to come get it?" the Westmoore High School Spanish teacher wondered.
"Even our insurance company said, 'you could pay someone to do it, but it might take days before they can come out here,'" Allison told CNN.
But for Allison, what seemed like a mammoth problem was swiftly solved on Sunday with the help of a group of students, parent-teacher association members and fellow teachers from his school and Heritage Trails Elementary, where his wife teaches music.
"We probably had 70 to 80 people in our front yard," he said, "and we cleaned it in a matter of 30 minutes."
Morgan DeLong, one of the volunteers, said many whose homes survived the storm are eager to chip in.
"It's kind of our turn to return that blessing and help people out. And it's incredible to be around all the faculty members and other students," she said. "It's amazing to just look out and see how our community's coming together."
As Obama got a firsthand look at the debris left by the tornado, the state's governor told CNN that her chief request for the federal government is help plowing through regulatory hurdles.
"Basically what I need is the ability to get through red tape, the ability to get the FEMA funds in here quickly and to get the services that our citizens need to help them recover through this terrible disaster," Gov. Fallin said on CNN's "State of the Union."
Fallin, a Republican, said the initial reaction from the federal government in assisting her state was fast and effective.
"So far we have had great response," she said, quickly adding there was a long way to go before Moore returns to normal.
"This is a massive debris field. It's not just a couple blocks," she said. "It's miles."
CNN's George Howell reported from Moore. CNN's Catherine E. Shoichet reported and wrote the story from Atlanta. CNN's Jeff Kepnes, Dana Ford, Rene Marsh, Nick Valencia, Kevin Liptak, Eric Fiegel, Greg Botelho, Mariano Castillo contributed to this report.