According to the Delaware County Daily Times, Sara Butler's lawyer says contradictory medications for lupus led the 44-year-old mother to think the world was ending.
Butler drove to Upper Darby High School in March with two adult children and a teenage son. She wanted to pick up another child, but the student wasn't released because Butler was not the custodial parent.
Police say family members then shed their clothes in the parking lot and chanted religious phrases.
Butler and her adult daughters pleaded guilty Monday to indecent exposure and related charges. All were placed on probation.