Philadelphia (CNN) — Seven teenagers were in custody Tuesday in connection with the beating of a 13-year-old boy, attacked while he was walking home from school this month in a Philadelphia suburb, authorities said.\nSix youths were arrested Monday at an alternative program at Upper Darby High School, Upper Darby police Lt. Thomas Sharp said. A seventh, who was absent Monday, was arrested Tuesday, he said. The 13-year-old and all seven suspects attended the alternative program, called the Opportunity Center.