Walter, 19, sits on a desk at Central Senior High School in St. Paul, Minnesota. Yasmin Yassin for NPR hide caption toggle caption Yasmin Yassin for NPR Before Walter even reached kindergarten, his teachers were kicking him out of class. " I kind of noticed that he was like really aggressive," his mom, Crystal Deramus, remembered. "Like, instead of him expressing himself, he throws things, he throws tantrums, he bites, he scratches … and the school started noticing too, and it just got worse." At home in Minneapolis, life was turbulent. Walter's father beat his mother and was in and out of jail before Walter even started school. Then, when Walter was just 5, Deramus was in a car wreck that left her in a wheelchair with paraplegia. She said that by kindergarten, Walter had gotten even wilder; he would run away from school whenever he got the chance. So she was relieved when his therapeutic day care recommended that he go to a high-security public school that locked its doors.…