Jason Messer started his public education career well aware that being a teacher could one day mean having to protect students from gunmen.The Manteca Unified School superintendent was a student at the University of Pacific when Patrick Purdy killed five children and wounded 29 others at Cleveland School in Stockton on Jan. 17, 1989. Then, later as dean at Lincoln High in North Stockton, a number of his freshmen and sophomores were students who had transferred to that school district after surviving the Cleveland School massacre.Friday’s massacre of 26 at a Connecticut elementary school prompted Manteca Unified to re-inform parents that there are contingency plans in place if the unthinkable happened here.Messer stressed that student safety is paramount. Teachers are regularly reminded of procedures plus pertinent information is posted in all classrooms.