Wednesday May 9th is National Bike to School Day, and before millions of kids across the country rush out the door, safety advocates are reminding parents to make sure they’re wearing a helmet. Dr. Marcee White, medical adviser for Safe Kids Worldwide, says preventable injury is the number one killer of children, and many are hurt on bicycles, skateboards and scooters. Her group surveyed parents about why kids aren’t wearing helmets, which can protect against serious head injuries and concussions. As for the kids, they said they don’t wear them because their friends don’t, or that the helmet doesn’t fit correctly. White says countrywide, 50 children are rushed to the emergency room every hour because of a preventable injury.