The president took a few questions from students at Long Branch Elementary School in Arlington. One child asked for an autograph, a request that was refused.
"Here's the thing," he said. "If I sign autographs, then I have to sign them for everybody."
Obama said he would have to stay at the school a long time to do that. When another child asked him how he found the time to write a book when he is so busy, he responded that he wrote most of the book before he was president and that it started as a letter to his daughters Sasha and Malia.
The president posed for pictures with the children, getting down on the floor with them and saying "Cheese."