The nation is still reeling from a shooting at a Parkland, Fla. high school last week that left 14 students and 3 teachers dead and injured more than a dozen others. It is the worst school shooting since the Dec. 14, 2012 massacre at Sandy Hook Elementary School that claimed the lives of 20 children and 6 adults. While school shootings appear to be dramatically on the rise, tallying the toll of these tragedies runs into the same problem as counting victims in mass shootings: What constitutes a school shooting?