The Ohio prosecutor calls it "bomb week," his shorthand for eight school threats - many written in school bathrooms or on notes - over a few days in May that set off evacuations and investigations, parental panic, and the rumor mill of students linked by cellphones and social media in Warren County.

The Ohio prosecutor calls it "bomb week," his shorthand for eight school threats - many written in school bathrooms or on notes - over a few days in May that set off evacuations and investigations, parental panic, and the rumor mill of students linked by cellphones and social media in Warren County.

Track athletes missed an end-of-season competition, and some high schoolers started carrying their car keys with them rather than leaving them in lockers, just in case, Warren County Prosecutor David Fornshell said. One mother complained that a girl who uses an insulin pump had taken it off for gym class and had to leave school without it.

"Nobody who sends their kids to school should have to go through that kind of stress and that type of disruption," Fornshell said.

Such violent or disruptive threats are increasing nationwide, according to police, school employees, security consultants and others. They are blamed sometimes on local students and sometimes on outsiders seeking to cause disruptions or a big emergency response.

State and local agencies don't track the threats, meaning that there's no formal accounting of the collective costs. The disruptions typically aren't long enough to merit makeup classes, but the learning time lost adds up, as do the hours that police spend responding and investigating.

"Schools are in a really bad position," said researcher Amy Klinger of the nonprofit Educator's School Safety Network. "People are going to be mad if you evacuate; people are going to be upset if you don't evacuate."

The number of school bomb threats in the previous academic year, based on media reports, was at least 1,267, roughly twice as many as in 2012-13, said Klinger, who also teaches educational administration at Ohio's Ashland University.

Her group estimates that the country had about eight bomb threats per school day last year, and that doesn't include other threats of violence and disruption. Massachusetts had the most bomb threats in that tally, 135, followed by Ohio with 96.

Because administrators and police can't ignore threats , they grapple with the fallout while trying to deter copycats.

In Ohio, more than 170 school threats were reported in the 2015-16 school year, according to an Associated Press tally based on police updates and media coverage. Threats of bombs, shootings and unspecified violence were called in, written as notes, scrawled on walls and shared via social media and apps.

More than 100 Ohio public school districts, or roughly one in six, dealt with at least one threat, as did a handful of private and charter schools and several college-level facilities.

In central Ohio, four Pickerington students were charged with felonies during one week in April for making similar but unconnected threats of violence at two high schools. Two students wrote threats in school bathrooms. A third student left a paper note in a school bathroom, and the fourth sent a threatening text message to students. Each threatened a bombing or shooting.

At least a couple of the recent Ohio threats occurred one day in late May when dozens of threats were made against schools nationwide as officials investigated whether it might be a case of "swatting," when hoaxers playing online games anonymously make threats online or by phone to trigger big responses from police and SWAT teams. Some of those schools were evacuated; others were not.

Ohio legislators have proposed letting schools expel students for months for making certain kinds of threats, and have the students evaluated to determine whether they're a danger to themselves or others. The bill, supported by associations representing school boards, superintendents and school business managers, also would let districts and law-enforcement agencies seek restitution from a student's parents for the costs of responding to their threat.

At least half of the Ohio threats last school year led to evacuations, dismissals or cancellation of classes or activities, according to AP's analysis.

And the prosecutor overseeing the "bomb week" cases is trying to drive home the point that even the false alarms have broad consequences.

A handful of students were blamed for those threats, including a 12-year-old girl. Fornshell said he will ask a judge to make those found responsible for evacuations hand-write apology letters to each of the hundreds of affected families in the district - perhaps 1,500 or more - in addition to serving time in juvenile detention or undergoing any other discipline.

Dispatch Reporter Alissa Widman Neese contributed to this story.