Parents in the Prior Lake-Savage school district are being asked to stop their kids from playing Nerf Wars, saying the game has become dangerous and disruptive to student safety.

In a letter sent to parents on Thursday, the Prior Lake school principal said the popular game, in which teams of students shoot foam darts at others to "kill" them in an attempt to win prize money, has led to confrontations in the Prior Lake High School parking lot, reckless driving in neighborhoods, threats on social media and students skipping school.

"This is a serious subject matter and we are asking you to help us by talking to your student and putting a stop to this game that has resulted in violations of school policies and criminal activity in our communities," the letter signed by Prior Lake High School Principal John Bezek and police chiefs in Savage and Prior Lake reads. "This game has become dangerous and, for the safety of all students, we are calling for a stop to Nerf Wars."

The game is normally played off campus in parks and other public places but has increasingly been infiltrating routines on campus.

Nerf Wars grabbed headlines in 2015 when Lakeville South High students Jacob Flynn, 17, and John Price, 18, were killed in a car crash while playing the game. Two other students were injured.

No charges were filed in the Dec. 4, 2015, crash. Parents of the young men killed sued the school district earlier this year for failing to protect the teens from a known danger.

In Thursday's letter, school officials stressed that Nerf Wars never have been a school-endorsed activity.

This is not the first time Prior Lake school officials have warned about the dangers of Nerf Wars and enlisted parents' help in stopping the game. Last year the school said in an e-mail that Nerf Wars can become dangerous when students get into vehicles and forget to buckle up, or don't obey traffic laws.

Thursday's letter said student safety is the district's and police department's top priority and that law enforcement and school administrators are conducting investigations that could result in criminal charges.