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(THE CONVERSATION) How many school shootings happen in the U.S. in a single school year? The answer is surprisingly hard to figure out.

In April, the U.S. Department of Education released a report on the 2015-2016 school year, stating that “nearly 240 schools (0.2 percent of all schools) reported at least 1 incident involving a school-related shooting.” However, the nonprofit Everytown for Gun Safety’s database lists only 29 school shootings for the same period.

When National Publi...