Police were called after the boy allegedly threatened to harm students with some sort of weapon, though police have not said what kind of weapon he claimed to have.
Officers arrived at the school and arrested the boy, who was booked into the King County Juvenile Detention Center. He's facing harassment and threats charges, police say.
After investigating the incident, police do not believe the boy actually had access to the weapons he claimed to have and did not represent an immediate threat to students or faculty members.
The school district exercised what they called "extraordinary caution" and placed the student on emergency removal pending a police investigation of the incident.