"You kids are the future of this great nation," Obama said to the crowd largely made up of military families and their charged-up children. "We need every American to serve their community, including our young people."
What can kids do? she wondered aloud: Volunteer in a homeless shelter, visit an elderly person or write letters to U.S. troops.
"For many of you, they're you're moms and dads, right?" Obama said. "Barack, Malia, Sasha and I are so grateful for the service and sacrifice all our military families make to help keep this nation safe."
Cyrus, who performed for the first time her inspirational song, "The Climb," returned the compliment to the Obamas' daughters, well-known fans of Cyrus' Disney TV alter ego, Hannah Montana.
"You girls must be awfully proud of your dad - and so am I," Cyrus said, inviting her father, Billy Ray Cyrus, to join her for a performance on stage.
Cyrus then went into the audience to quiz kids on some history: What was President Ulysses S. Grant driving when he got the first-ever presidential speeding ticket? The crowd correctly picked a horse and buggy over a skateboard or Ferrari.
"You didn't think we can give you a quiz on a day with no school? We say, `Yes, we can!" comedian George Lopez joked with the crowd that also included local families who received tickets from the Boys & Girls Club of Greater Washington.
The Jonas Brothers got Obama - wearing a sparkly blue dress and mustard-yellow cardigan - on her feet dancing, and Malia and Sasha to come up on stage to jump around like the schoolgirls that they are.
