The nation’s two largest teachers unions want schools to revise or eliminate active shooter drills, asserting that they can harm students’ mental health and that there are better ways to prepare for the possibility of a school shooting. The American Federation of Teachers and National Education Association joined with the advocacy group Everytown for Gun Safety Support Fund in calling for an end to unannounced drills or drills that simulate gun violence. The report released Tuesday recommends schools concentrate on training teachers to respond to an active shooter incident rather than drilling students. It also issued guidelines for schools that decide to use drills. Those include never simulating an actual shooting; giving parents, educators and students advance notice of any drill; working with mental health officials to create age-appropriate and trauma-informed drills; and tracking the effects of drills. Still others say that active shooter drills are effective when done appropriately. Some experts believe that simulating an event is the best way to prepare for one. According to a survey by the National Center for Education Statistics, about 95% of schools drilled students on lockdown procedures in the 2015-16 school year.