As summer ends and students head back to school, we dedicate this hour of Midday on Health with Dr. John Cmar of Sinai Hospital to surveying health issues that affect young people. First: binge drinking and habitual marijuana smoking are becoming more prevalent among college and teenage students. Parents and pediatricians are urged to speak with children about the dangers of alcohol early--by the time the kids are 9. Then, put down that water! We’ll hear why athletes tend to over hydrate, and why that’s risky. Plus, after the national measles scare last spring, an update on school vaccination policies and the controversy around them.