Schools around the region said Thursday they were taking extra precautions and stepping up police presence because of TikTok posts shared across the country warning of threats to schools on Friday.

In messages to parents, school officials cited the wider national trend of school-related “challenges” and threats posted on the social media platform this fall that have been credited with spurring vandalism and havoc in schools.

They said the threats about Friday hadn’t originated in their districts, but many still were communicating and coordinating with police. State law enforcement is also involved: A spokesperson for Attorney General Josh Shapiro said officials met with representatives from TikTok’s parent company Thursday to discuss the threats.

“The Centennial School District has become aware of a troubling post that has been shared widely this week on the social media platform TikTok,” Dana Bedden, superintendent of the Bucks County district, told parents in a message. “The post refers to a threat to school safety ‘for every school in the USA, even elementary,’ on Friday, December 17.”

In the Garnet Valley School District, a message Wednesday from Superintendent Marc Bertrando alerted parents that students and teachers shared a TikTok post with administrators “that stated verbatim: ‘For anyone wondering on the the 17th, there will a massive school shooting threat across america not 100% sure but there’s a possibili.’ Another part of the story read, ‘on friday there is supposed to be a massive school sh00ting threat across america.’”

While the post didn’t have to do with Garnet Valley, Bertrando said in an interview that he wanted to share everything the district knew before a rumor could start that “creates such an uproar in the community that there’s no way to pull it back.” Like other districts, Garnet Valley has faced social media threats recently — including what officials described as a “terroristic threat” last week involving the middle school — and Bertrando said families were “rightfully anxious” around the prospect of violence.

The district planned to permit absences for children whose parents keep them home Friday, Bertrando said — a choice he said families should have, though he also felt that keeping schools open was an important deterrent.

“What I don’t want to do is set up scenarios where these kids who want to create pranks or hoaxes to get out of school” succeed by making threats, he said. He said Pennsylvania State Police would be increasing patrols Friday.

State Police officials from Troop K, which covers Philadelphia, Montgomery, and Delaware Counties, said that they will be monitoring school districts Friday morning and providing added presence as requested by administrators.

In Upper Darby, Police Superintendent Timothy Bernhardt said that the threats have been investigated by detectives, and that no direct connection has been found to the Delaware County district. “From our standpoint, it looks like it’s a national threat,” Bernhardt said. “So we will have an increased presence at the schools.”

Bernhardt said the threat, like others the district has received recently, was taken seriously and vetted by police analysts. Upper Darby’s superintendent coordinated with him in issuing a warning to parents after seeing other schools do the same.

“Parents, we are asking for your help,” Superintendent Dan McGarry wrote in that warning. “We are asking that you talk with your children about social media and urge them not to take part in these unsafe behaviors.”

In Philadelphia, district officials informed parents of posts circulating on TikTok and asked parents who learn of any threats to share information with school leaders — and to talk with their children about the importance of “not participating in or promoting any threats of violence.”

Other districts connected the TikTok posts to threats in their communities. The Haverford Township School District in Delaware County cited TikTok when it told parents that it had discovered writing on a bathroom wall in Haverford Middle School warning of a possible shooting in the school on Friday — calling it likely a “copycat message.”

While it said police don’t believe students are in “any immediate danger,” the district said it would have extra security during Thursday’s dismissal and increased police presence Friday to take added precautions.

Upper Dublin also planned more police in its schools. Superintendent Steve Yanni shared that precautionary step as he informed parents of “another TikTok challenge/threat” — and that police were investigating a message discovered on a bathroom wall at Sandy Run Middle School.

In Cheltenham, school officials said Thursday they also confirmed that a threat left on a bathroom wall at the high school last week warning of violence Friday was part of that TikTok trend.

The district had previously told parents that police were confident the threat wasn’t credible, but said that law enforcement would still be present “inside and outside of our building for the entire day.”

Staff writer Kristen A. Graham contributed to this article.