Cops were called to Mark Twain Elementary School after the boy was pricked by the hypodermic needle.
The child underwent testing for communicable diseases, authorities say.
In a statement posted on Facebook, Carson City Sheriff’s Office said: “School officials at Mark Twain Elementary School took immediate actions to secure/safe the playground areas. Other items, including alcohol containers were located and secured for officers. Classroom activities at the school continued as normal and students were released on time at the end of the school day. “
The matter is still under investigation.