Tamworth: Police will be on guard at a school where voters will lodge ballots on Saturday to decide whether to return Nationals leader Barnaby Joyce to Parliament after a bullet and a threatening note were reportedly found on the school's premises.

A bullet was also sent to Mr Joyce's former electorate office in Tamworth, though local police reportedly said they believed the latest incident was related to the school itself, not to the election campaign.

Barnaby Joyce, pictured near Tamworth, NSW. Credit:Simon Chamberlain

Fairfax Media understands a threatening piece of writing with the latest bullet, found 10 days ago at a school in the town of Quirindi, south of Tamworth, warned there would be a shooting on December 2, the date on which the New England byelection is being held.

"Police of Oxley local area command are investigating after the discovery of an item and graffiti at an education facility in Quirindi," NSW police said in a statement.