Chicago Public Schools can’t be sued for an off-campus bullying attack, a state appeals panel ruled Tuesday.The 1st District Appellate Court upheld the dismissal of a lawsuit brought against the board of education for allegedly failing to protect a student from a bully on and off school grounds.Plaintiff Elizabeth Castillo, a student at North-Grand High School in Humboldt Park, alleged she was repeatedly bullied by schoolmate Estrella Martinez, culminating in a physical attack in January 2015 just off campus.She and …