WASHINGTON — One in every 5 middle and high school students has complained of being bullied at school and the number of reports of sexual assault on college campuses has more than tripled over the past decade, according to a federal study released Tuesday."There are areas of concern in terms of bullying and rates of victimization being high," said Lauren Musu-Gillette, one of the authors of the report by the National Center for Education Statistics and the Justice Department. "We are seeing a long term decline, but we still want people to be paying attention to areas where rates are still high."Even though the overall prevalence of bullying has been declining in American schools over the past decade, 21 percent of students aged 12-18 reported being bullied in 2015, the report found. That was slightly below the international average."Bullying is a public health issue because it really affects the mental wellness and health of students and as we know at the extreme end it can lead to everything from suicide to reactive violence," said David Osher, vice president at the American Institutes for Research.