Ninth-grader Yaretzi Perez wants to be a neonatal nurse. But first, she has to find a way to stop missing so many days of school. Her mother, Eleuteria Perez, is a single parent of five — ages 17, 14, 13, 10 and 8. They attend four schools, all starting at the same time. She’ll sometimes arrange a pick-up; sometimes pay someone to help. But the two older girls were supposed to walk to their...