Northwest High School Credit: Via Montgomery County Public Schools

Updated at 5 p.m. Friday: A 15-year-old student at Northwest High School in Germantown has been arrested in connection with an online threat against the school, Montgomery County police said.

The boy was charged with disrupting the school, Capt. Paul Starks, a police spokesman, said Friday afternoon. Police do not identify offenders charged as juveniles.

Starks said the threat, which was a social media post warning Northwest students not to come to school, was one of a string of similar threats reported Friday, with “10 to 12” schools receiving some type of threat.

The threats were posted online through social media or, in some cases, shared over text, he said.

“They’re all different, but they involved a threat to safety and the education process. … Warning people, “Don’t come to school,” “there’s a gun,” or that kind of thing,” he said. “Many of these kids think it’s a joke, they do this on a lark. They press send or post and don’t really think about the consequences or ramifications.”

The threat comes a day after a Clarksburg High School student was charged with bringing a loaded handgun to school, and two days after a former student shot and killed at least 17 people at a high school in Parkland, Florida.

Starks said schools are not considered to be in danger, but that police “do not have the luxury” of not taking all of the threats seriously and were investigating each one. Charges had not been filed in connection to any other threat as of Friday afternoon.

Starks said police were not naming the other schools that had received threats, but said most were high schools, except for one middle school.

Northwest High School stepped up security Friday as a precautionary measure after the threat. Principal Jimmy D’Andrea wrote in a message to the school community that another student had alerted authorities around 3 a.m. to a social media post warning Northwest students not to come to school.

Police do not believe the threat was credible, D’Andrea wrote on Twitter.

Police officers increased their presence at many schools Friday, which Starks said was an effort to let parents know that they were aware of the threats and and “to give them comfort that it was a safe environment” and also respond to any questions parents might have.

He said county police have seen similar threats issued after school shootings became national news in the past. Though the threats are not necessarily credible, Starks said it’s important for students to notify authorities about anything they hear related to a threat.

“If they see something, they shouldn’t assume that it’s not real or that the person is joking. They should go to their parents, they should go to school administrators, or they can even call police themselves,” he said. “Then if it is real, we can prevent it.”