Last year, 93 bicyclists under age 15 were killed and 12,500 sent to emergency rooms, according to the National Highway Traffic Safety Administration. Head injuries accounted for 63 percent of all bicycle fatalities. "California state law requires that all children under 18 wear a helmet when they are riding a bicycle, scooter or skateboard. If a child has an accident, a helmet can prevent a serious brain injury," said Jeffrey Upperman, MD, medical director for the Pediatric Trauma Center at Childrens Hospital Los Angeles. According to the Bicycle Helmet Safety Institute (BHSI), all helmets sold in the U.S. must meet test requirements from the Consumer Product Safety Administration. Size is a key factor, since children grow rapidly. The helmet should be comfortable, but fit snugly. The BHSI advises that in terms of safety, there is no difference between a $20 helmet and a $120 one. The National Highway & Transporation Safety Administration publishes Easy Steps to Properly Fit A Bicycle Helmet . Their 6-step worksheet makes it easy to properly fit your child's bike helmet. So, before your child rides his/her bike to school, make sure the helment fits! Print out several copies of the NHTSA guide - one for yourself and extras for your child's classmates!