Sixty years to the day after Rocky Marciano raised his arms in victory over Joe Walcott, a 21.5-foot statue of the undefeated heavyweight champion will rise on the grounds of Brockton High School. The dedication of the long-awaited statue, a gift from the World Boxing Council, is set for Sept. 23 at 1 p.m. “We think it’s the largest sports statue in the country,” said Lawrence Siskind, chairman of the Rocky Marciano Statue Foundation. The group has raised money to prepare Champions Park, the statue’s home. The statue is on its way from Mexico, where it was sculpted, and will arrive about Sept. 1. The school’s football stadium is named for Marciano, a Brockton native. For more information or to donate or buy a commemorative brick, visit www.rockystatue.org.