title: Unschooled in hard knocks.
mesh_terms: D000293:Adolescent; D001265:Athletic Injuries / Q000150:complications / Q000453:epidemiology*; D001924:Brain Concussion / Q000150:complications / Q000175:diagnosis / Q000453:epidemiology*; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D008297:Male