District spokeswoman Sandi Beason says the gun was discovered Friday afternoon when the student showed it to another child, who then reported it to the school. The school has classes for fourth and fifth-graders. She did not know whether the gun was loaded.
Local police are investigating. Certified police officers work on the school campuses in Clinton, a suburb of Jackson.
State law says any student with a gun, knife or other weapon on campus can be expelled. The student also has the right to appeal the expulsion.