That was the sickening — and urgent — question that many Chicago parents and students asked in June after the Tribune’s “Betrayed” series found that at least 72 CPS teachers, coaches, lunchroom aides, counselors, security officers and deans had been accused of sexually abusing students over the past decade. Several of those accused had criminal backgrounds that should have disqualified them from working with students — one had felony drug convictions, another was convicted of a sexual crime involving a child after he was hired.