Complex sentence: Two former students had allegedly lodged complaints about Lynch's conduct with then headmaster of the school, Maxwell Howell, in the early 1980s and the issue was quietly investigated, however Grammar was unaware the details had to be passed on to its insurer.
Split into simpler sentences: Two former students had allegedly lodged complaints about Lynch's conduct with then headmaster of the school, Maxwell Howell, in the early 1980s and the issue was quietly investigated. However Grammar was unaware the details of the investigation had to be passed on to its insurer.