A long-buried report shows that the principal at a Chicago elementary school “knew or should have known” about a teacher who was accused of sexually abusing at least 19 boys. A new Chicago Tribune investigation has found a lengthy 2002 case manager’s report from the Chicago Public Schools’ inspector general’s office, which is said to have concluded that at least four CPS employees reported their concerns about Marvin Lovett while he taught at the school. Lovett for years made secret pornographic videotapes of young students. In 2000, Lovett was shot to death by a student he had abused for at least five years. The principal, Mattie Tyson, according to the report, “had reasonable cause to believe that children known to her in her professional or official capacity may have been abused.” Her lack of action amounted to a violation of state law and CPS policy, according to the document.