Castelberry High School in Fort Worth is on lockdown after a student reported seeing another student with a gun, superintendent Gary Jones said.
The campus was placed on lockdown while a locker-by-locker search was conducted and while the student said to have the weapon was questioned.
Officials said nothing was found on the student, but that an air pistol matching the description of the weapon was found in an unlocked, empty locker.
Officers continued to search every locker in the school to make sure there are no other weapons on campus -- none were found.
The lockdown was later lifted and the school dismissed students on time.