Imagine you open the door to a classroom of 30 students. About 14 students in the room will experience sexual harassment in the coming school year - eight girls and six boys. Four of these students will not want to come to school at some point during the school year as a result of sexual harassment. For three students, these feelings will last a short time, but for one student, these negative feelings about school will last “for quite a while.”

Female students are especially at risk. Assuming 15 girls are in the class, approximately two girls will have trouble sleeping and three will feel sick to their stomachs as a result of sexual harassment.

In the 2010 – 2011 school year, this classroom was typical, according to a recent American Association of University Women (AAUW) report, Crossing the Line: Sexual Harassment at School, published last week. As a co-author, I am proud of this new resource, which provides the most in-depth, nationally representative data on this subject in more than a decade.

A few issues struck me in the course of analyzing the data for this report. The first was simply the sheer number of children who have to deal with this often painful and humiliating experience. If this year is anything like last year, nearly half of American students will be sexually harassed at school between the beginning of classes in the fall and the end of the school year in the spring.

Much of the sexual harassment will be verbal and in person, but nearly a third of students will experience some form of cyber harassment. For the most part, cyber harassment appears to happen in concert with in-person harassment. This combination seems to be the most damaging. Students who were harassed online and in person were significantly more likely to report negative effects as a result of their experiences than were students who were harassed only in person.

Sexual harassment is not just an issue for girls. Boys, too, encounter unwanted sexual conduct, and many experience negative effects as a result. “Being called gay in a negative way” was a common form of harassment among boys and the form that boys identified as the “most negative experience” for them. “That’s so gay” and “you’re a fag” are common statements at middle and high schools. These taunts are often directed at straight students as well as students who are perceived to be gay.

Students apparently use these homophobic slurs against any peer who in some way fails to meet the social gender norms. The departures from gender norms can be minor, such as girls playing sports or boys wearing colorful clothing. A great source for information on “gender policing” among middle and high school students is the organization TrueChild. This website offers insight on the phenomenon, including ideas for prevention. Stopping gender harassment is not simply a matter of rules and enforcement - we need to change attitudes.

That is a tall order. But luckily, we have prosaic steps that can also make a difference. More than one-third of students surveyed said that they thought it would be useful to have a teacher or guidance counselor as a contact for this issue. The good news about this recommendation is that every school should already have a Title IX coordinator in place. The 1972 law protects students from sexual harassment and ensures equal opportunities for girls in sports and academic programs.

But too often, the Title IX coordinator is overwhelmed with myriad responsibilities. Students are not aware of this resource and even teachers may be in the dark. The administrators or teachers designated as Title IX coordinators need the time and tools to prevent sexual harassment and respond to the problems at hand.

For too long, sexual harassment has indeed been just part of school life, an invisible problem to adults and an intractable one to students. Let’s make it visible. And then let’s put a stop to it.

Catherine Hill, Ph.D., is the director of research at the American Association of University Women and the co-author of Crossing the Line: Sexual Harassment at School.

All statements and opinions expressed on this blog are those of the individual contributors, and not of the Bill & Melinda Gates Foundation or NBC News.