The Joplin twister was the country's deadliest single tornado in six decades. Beyond the dead, hundreds more were injured and thousands of buildings were destroyed, including Joplin High. Five other Joplin schools were also destroyed, with four more among the damaged structures.

The twister arrived hours after last year's high school graduation. Will Norton, a member of the 2011 graduating class, was killed, as was Lantz Hare, who would have graduated next year.

"You've learned at a younger age than most that you can't always predict what life has in store," Obama said. "No matter how we might try to avoid it, life surely can bring some heartache. And life involves struggle. And at some point, life will bring loss."

Obama traveled to Joplin in the days after the tornado struck, meeting with residents and viewing the devastation.