A 10-year-old Malcolm Roach stood on the sidelines in full pads as the chatter began building. It was the fourth quarter of a Southern Lab University School varsity football game in 2008, and the Kittens — coached by Malcom’s dad, Mike Roach — were up by more than 50. Bigger than most kids his age in Baton Rouge, La., Malcolm was certain he could hold his own against high school players — even as a fifth-grader.