Four hundred students have been playing a game of Assassin in the hallways of Montgomery County’s largest high school this fall, an annual tradition of sorts that has largely fallen under the radar until now.

The student-organized game at Montgomery Blair High School involves no real violence, and supporters liken it to a complex game of tag. But its talk of killing targets and stalking classmates comes at a time when many school systems have increased security, added police and locked buildings in the wake of the real-life horrors of school shootings.

In the year since a gunman killed 20 children and six staff members at Sandy Hook Elementary School in Newtown, Conn., educators have grown especially sensitive about guns and potential threats, and there have been several high-profile disciplinary cases in the Washington region, including first- and second-graders who were suspended from school for pretending to shoot others with their fingers or, in one case, a breakfast pastry.

Nationally, many schools have been increasingly vigilant, even in cases that were apparently playful. In Montgomery County, administrators suspended a 6-year-old from a Silver Spring elementary school last December for pointing his fingers like a gun and saying, “Pow!”

Blair, also in Silver Spring, comes as a counterpoint. On the campus of 2,800 students, Assassin is especially big this year, and while school authorities have not interfered, they say they are now examining it. Not everyone likes its language or name, but others say it brings students together in a strategic challenge.

“Unfortunately, it’s easy for students to forget, when they are wrapped up in the enthusiasm of the moment, what the specifics of the game might mean to someone looking in from the outside,” said Blair English teacher Jeremy Stelzner.

The game works like this, according to a student: An “assassin” approaches a target, touches the person and uses the catchphrase: “Your a-- is grass, and I’m the lawn mower.” The target avoids demise only if someone else steps forward and says “Witness.” The Washington Post is not identifying the participant because he is a minor and his family asked that his privacy be protected.

The game caught on quickly in November, with 400 students signing up in three days as word spread over Facebook. A few weeks later, it was profiled in the student newspaper, Silver Chips, which called it a massive contest of “wits and treachery.”

Since Assassin began, “the tension at Blair is palpable,” the Silver Chips story reported. “Many players take extra precautions during school hours, keeping witnesses close by in an attempt to avoid early elimination.” One student said he tries to never walk alone.

The game is similar to others that have been played on college campuses for years, some of them based on the 1980s role-playing guide by Steve Jackson called “Killer: The Game of Assassination.” Versions of the game have been appearing in some of the nation’s high schools in recent years, according to news reports.

Dylan Ahunhodjaev, 16, who wrote the Silver Chips article, said the game appears to have a bonding effect on the campus but that the name grabbed his attention. “I know it’s jarring,” he said. “When I heard it, I thought, ‘What?’ ”

Principal Renay Johnson said the school neither endorses nor sponsors the game, and she said she has never seen Assassin being played and only recently learned of it. She said she does not want it at Blair and pointed out that weapons cannot be used even in school plays. “I don’t think a game called Assassin is appropriate in schools,” Johnson said, adding that she plans to meet with students and teachers to discuss it. “I want kids to be social with each other, but not in a ‘gotcha’ . . . sort of way. It’s just inappropriate in our society.”

Johnson said that the game, which is voluntary, has not led to disciplinary issues or other problems and that no one has reported feeling unsafe or threatened.

Although the game is popular among students, there are others in the school community who don’t embrace it, especially in light of Newtown.

“I think it’s an adolescent brain at work — not understanding the implications of what an assassin is,” said Therese Gibson, president of the Parent Teacher Student Association at Blair. “They’re not thinking of what those words stand for.” Gibson emphasized that Blair is a safe school, with a strong security presence, and said any real threat would be intercepted quickly. “It’s almost as if this was a video game being played off-screen,” she said.

In the post-Newtown world of school safety, some see the issue as problematic.

“School should be a ‘safe’ place where games like Assassin should not be played and probably should be forbidden,” said Susan Burkinshaw, co-chair of the health and safety panel of the county’s council of PTAs. At a minimum, she said, parents should be informed and asked for their consent.

Robin Ficker, the attorney for the Montgomery child suspended for pointing his fingers like a gun, warned against overreactions to finger guns or other activities he said amount to children at play. “It seems harmless, ” Ficker said. “It’s role-playing.”

Montgomery schools spokesman Dana Tofig said principals make decisions about student actions in their buildings, with a review process available. The 6-year-old’s suspension was appealed and his record was cleared. “They are different cases,” he said.

Some educators at Blair have complained about the game, said Stelzner, the English teacher who is adviser to the print edition of the student newspaper and who finds the game’s language insensitive. “We go to such great lengths to protect kids, and to have a game where you’re playing around with that idea, it doesn’t make sense to me,” he said.

At Blair, about 100 students were eliminated in the first week, according to a participant. As the number of players dwindles daily, students guess the game might be over around winter break.

Jennifer Jenkins contributed to this report.