CNN 10: The big stories of the day, explained in 10 minutes

Teachers, as always we recommend you preview each episode of CNN 10. Part of our headlines today involves coverage of school safety concerns following news out of Nashville this week. Today CNN 10 is looking at headlines from around the world. The U.S. and South Korea have re-started joint military drills on the Korean Peninsula. A tragic event in Nashville has sparked further debate over gun control laws and school safety. And in the art world, scientists say they've identified a secret ingredient in Leonardo da Vinci paintings. And in Australia, a group of heroic volunteer firefighters are willing to risk their lives to keep others safe. All that and a group of celebrity ducks who are treated like royalty on this episode of CNN 10.