Understanding the scope of the problem of guns in schools is made more difficult by inconsistent data collected by state and federal officials.

A combination of state and federal data shows hundreds of cases involving guns, children and schools in recent years.

There were 470 incidents involving a real gun reported in Tennessee schools from the 2011-12 school year to 2017-18, according to the Tennessee Department of Education. That’s about one real firearm — as opposed to a BB or toy gun — at a Tennessee school per week during that time period.

The department is required to track gun incidents at schools under a federal education law. That same law insists states report that data to federal education officials.

However, U.S. Department of Education statistics reported 46 more gun incidents than local officials from the 2011-12 school year through the 2015-16 school year.

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“We reported accurately the numbers that were reported to us at the time. We rely on districts to share this information correctly," said Sara Gast, a spokeswoman with the Tennessee Department of Education.

"We provided districts the opportunity to double-check what was reported given the additional level of detail (requested by the USA TODAY NETWORK - Tennessee), which resulted in some incidents (e.g., toy guns) being coded differently and withdrawn from the data."

Gast also noted some schools — she did not say how many — told the state their incidents involved students who accidentally left guns in their cars after using them for hunting.

A Public Broadcasting Service report in March showed how many states failed to accurately report incidents of guns at schools, as is required by federal law.

A National Public Radio report in August revealed how unreliable federal education data on school shootings can be. While the U.S. Department of Education stated for the 2015-16 school year that “nearly 240 schools” reported a school-related shooting, NPR could corroborate only 11 of those incidents.

From 2001 to 2017, Tennessee law enforcement reported 1,690 weapons law violations involving a gun at a school, according to available data from the Tennessee Bureau of Investigation.

More than half of the incidents occurred in Shelby and Davidson counties, home to Memphis and Nashville. But 20 other counties reported at least 10 incidents during the same time frame.

The TBI data covers a much longer time frame than data available from the state Department of Education.

The TBI data does have some flaws. The USA TODAY NETWORK - Tennessee analysis of 300 police reports included among those incidents determined about 71 percent of the reports involved a real firearm, 21 percent referenced a toy or air gun — typically a BB gun or pellet gun — and 7 percent mentioned a weapon that was not a gun.

The state education data should not include any air guns or toy guns, Gast said.

A few police reports included in the TBI data listed addresses that do not correspond to a school.

It wasn’t immediately clear how many of the remaining incidents involved toy guns or air guns, no guns or did not occur at a school. Many law enforcement agencies refused to provide reports to the USA TODAY NETWORK, saying documents could not be released because juveniles were involved.

The Memphis Police Department provided most of the reviewed reports. Another 21 law enforcement agencies also sent reports.

Reporter Jordyn Pair contributed to this report.