A five-year-old boy was found with two gun cartridges at a primary school in Clacton-on-Sea, Essex.
Teachers at the school made the discovery and called the police.
They seized the cartridges and spoke to the pupil and his family.
Police refused to disclose where the incident took place or how the pupil came to be in possession of the ammunition.
An Essex Police spokesman confirmed the gun cartridges were confiscated.