Washington - One in every five 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 US federal study."There are areas of concern in terms of bullying and rates of victimisation being high," said Lauren Musu-Gillette, one of the authors of the report by the National Centre 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% 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. "Because it happens, it doesn't mean it has to happen."'Homophobic bias'The picture was bleaker for gay, lesbian and bisexual students. A total of 34% of students who identified as LGBT complained of bullying, compared to 19% who identified as heterosexual."It's a high number and a disproportionate number in comparison. We still have a lot of homophobic bias and it plays itself in schools," said Charol Shakeshaft, an education professor at Virginia Commonwealth University. "Those students are singled out and isolated and harassed."Shakeshaft lamented the Trump's administration decision earlier in 2017 to rescind Obama-era guidance on the use of bathrooms and other facilities for LGBT students, which she said helped them feel safer. When rescinding the guidance the Education and the Justice departments said such decisions should be left to the states.Osher said campaigns to raise awareness can only help so much in helping to fight bullying. He called for programmes that build empathy and self-awareness, identity and provide support for students who have mental health problems and foster a positive climate in schools.