Student Bryan Holley was taken into custody just before midnight. Deputies said they learned of the threat Monday evening.
An arrest warrant said Holley said on Twitter that he was going to "do a mass shooting at Richlands High School and everyone should wear bulletproof vests."
Holly is charged with making a false report of mass violence on education property.
The sheriff's office said additional officers were assigned to provide security at the school on Tuesday as a precaution.
Another teen is also charged after a separate incident at Southwest High School in Jacksonville.
Student Kyle Szuch is accused of making a bomb threat at the school Friday.