More than two-thirds of high-school athletes who suffered concussions reported playing with symptoms, according to a study by the University of Washington Schools of Public Health and Medicine. The study, published in the American Journal of Sports Medicine, followed 778 male football and female soccer athletes through the fall 2012 season in 20 rural and urban high schools. The incidence of concussion was more than 10 percent among all athletes. Of those, 69 percent reported playing with concussive symptoms – such as headaches or dizziness – while 40 percent said their coach was not aware of their concussion.