The deadliest school shooting in nearly a decade, and what’s changed in the years since the massacre in Newtown, Conn. Read more:Washington Post reporter Arelis Hernández is on the ground in Uvalde as children and families try to make sense of the violence that tore through Robb Elementary School on Tuesday. According to a Post database,last year was the deadliest year for school shootings in America since at least 1999, the year of the Columbine massacre. This year is on track to be even worse – and the reasons for that aren’t entirely clear. John Woodrow Cox, who helped create The Post’s tracker, breaks down the massive, sometimes unseen impact of gun violence on American schoolchildren, and the tricky politics of gun control legislation.Read an excerpt from John’s book, “Children Under Fire: An American Crisis.”