Spectator Olly Croker was watching his brother play in a match in Devon on 12 September when two players collided with a safety fence, said witnesses.
A post embedded itself in Olly's head in what was called a "freak accident" by host club Bradninch.
Shops, businesses and schools closed early for the funeral in Bampton.
More than 500 people joined a cortege to St Michael and All Angels Church in Bampton.
Vicar, the Reverend Kevin Chandra, said: "So many groups of people have come together to give their best to the family, to support them and give them courage on a really terrible day."
The funeral cortege was led by an Aston Martin sports car, with Olly's twin brother Billy in the passenger seat.
The circumstances of Olly's death are being investigated by police and local authorities.
The Tiverton High School pupil was watching a game between Bradninch and Bampton when he was struck. He was taken to hospital but died two days later.
Writing on Facebook after his death, his mother Pippa described him as a "gorgeous boy", and said he had "given life to 5 other children" through organ donation.
Head teacher Andrew Lovett described the schoolboy as a "larger-than-life character" and expressed his "great sadness" at Olly's death.
Hundreds of people have attended the funeral of a 12-year-old football fan who died after he was struck by fencing during a game.