Unlike colleges and universities, there are no national requirements for U.S. elementary and secondary schools to track student sexual assaults. But 32 states and the District of Columbia do maintain information, though it is inconsistent and sometimes incomplete, The Associated Press found.

Some states required school districts to log any student sexual assault on school property or at school-sponsored events, but others required reporting of only those assaults resulting in certain types of student discipline. In Michigan, for example, the state counted only expulsions. So one Lansing high school was able to report no sexual assaults in 2015 while AP found a case in which a student was suspended and later charged with criminal sexual conduct. Additionally, some states masked the actual number of student sexual attacks if they fell beneath a certain threshold.

Whether and how an incident was recorded — as sexual assault or something less serious — was often left to school districts’ discretion. Education officials in a half-dozen states told AP they didn’t think their data reflected the full extent of the problem. In addition, some of the nation’s largest school districts — including those with student enrollments over 100,000 — reported no rapes or sexual assaults for multiple years, even though AP identified cases through public records or news accounts.

Student sex assault records and training

32 states and D.C. track student-on-student sexual assaults. States also varied widely in their methods to stop or address the assaults.

SOURCE: AP survey of state education departments, 2011-2015

In the 18 states with no reporting requirements, cases can go unnoticed, such as the 2010 sexual assault of a girl in a Muncie, Indiana, high school bathroom, which resulted in a boy’s guilty plea.

AP compared state education agency information from fall 2011 to spring 2015 — across the four academic years for which most reported — counting only the most severe forms of sexual assault, such as rape, sodomy, forced oral sex, penetration with an object or unwanted fondling.

For states with no education data, AP looked to the National Incident-Based Reporting System, a database of participating states’ crime reports collected by the FBI. AP used the two most recent publicly available years of NIBRS data — 2013 and 2014.

By mining those records, the AP was able to uncover about 17,000 official reports of student sex assault — an undercount due to the significant under-reporting and spotty categorization.