The juvenile, whose name was not released, was charged with first-degree threatening and second-degree breach of peace, Ridgefield Police said.
The Ridgefield HS school resource officer was notified of the threat referencing a firearm and written in a girls bathroom at around 9 a.m., police said.
The Ridgefield Police Department, with assistance from the New York State Police K9 Unit, conducted a sweep of the Ridgefield High School which produced negative results.
The teen is scheduled to appear at Bridgeport Juvenile Court on Monday, June 10.
"This morning, Ridgefield High School received a written threat," the district posted on its website. "Administration and police responded immediately. Out of an abundance of caution, we are dismissing RHS at 9:30 a.m.
"This dismissal (and the threat) does not affect Scott’s Ridge Middle School."
Click here to follow Daily Voice Pound Ridge and receive free news updates.