More recently, Valerie Adams was just 15 years 5 months when she competed in her first New Zealand senior women's shot put championship.
Walter Gill, father of Jacko and twice New Zealand senior men's shot put champion, says that Jacko might bypass the New Zealand championships if he is not permitted to compete in the senior men's shot and head to the Australian championships instead.
"Come March, Jacko might still need a back-up performance with the senior weight shot to confirm his selection for the London Olympics," Gill says. "The Australians have no such rule precluding an athlete of Jacko's age from competing in their senior championships. I know he would be welcome over there.
"While Athletics New Zealand has done much to promote and develop our sport in more recent years, this latest rule is ridiculous."
Gill isn't the only athlete affected by this rule. Depending on their birthdates, up to a dozen teenagers who competed brilliantly at last weekend's New Zealand secondary schools' athletics championships in Wellington could also be affected.
They include Kodi Harman, winner of the senior boys' 100m-200m double in 10.67s and 21.39s, Andrew Whyte (400m in 46.91s), Brad Mathas (800m in 1m 50.24s), Rebekah Greene (1500m in 4m 21.39s and 3000m in 9m 23.42s), Nicholas Southgate (pole vault of 4.90m) and Julia Radcliffe. All six broke New Zealand secondary schools' records and would be more than competitive against senior athletes.
Gill, meanwhile, will attempt to improve his own national senior record of 20.34m and again better Athletics New Zealand's Olympic qualifying standard of 20.30m at the Millennium Stadium on Auckland's North Shore tomorrow night, starting at 5pm (weather permitting). Gill might also attempt the world junior (under 20) record of 22.73m held by this year's world champion David Stohl of Germany.
He will have a final competition on Thursday night, again at the Millenium Stadium, where he will try to break his own world youth (record) with the 5kg shot before going into build-up phase for competitions in March and the Olympics.
Athletics New Zealand chief executive Scott Newman says the rule was introduced at the behest of clubs around the country and drew only one objection through the consultation process. It's designed to discourage young athletes from training at adult intensity during their formative years.
But he insists the door is not closed on Gill contesting the national senior title.
"Any athlete can apply to the Athletics New Zealand board for dispensation," says Newman. "If Jacko thinks throwing the senior-weight shot is important to his build-up for the Olympics, I'm sure the board wouldn't deprive him that opportunity."