Mackenzie Haitsma is 15, and she will not turn 16 until December 27. She met two out of three relative age effect requirements set out by Capital Football to play down a year, with weight deemed the factor that will prevent her from playing in the under 15s competition.

Her mother, Tamara Haitsma, wants to know why the 50th percentile is still being used, and why weight plays a part given the effects on body image.

She said they had reached out to other clubs to see if any had similar stories.

"Our big concern here is that this has happened to other girls as well. We're just trying to work out how many other girls have been affected and have left the sport because they've been told 'No, you don't hit the 50th percentile. You're too big'," she said.

"That's actually a ludicrous and outdated kind of way of looking at things. You can't say that. You can't do that, especially not in 2022.

"She has to be smaller than 50 per cent of the kids to be considered, despite the fact that she's born just four days before the end of the year.

"The ridiculous part about it is if you put my child on the field in a training situation with the rest of our team, you would not be able to pick out that she's the eldest out there, not by a longshot."

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RAE's are used for players who from a physical stand-point (height, weight, speed, strength) are disadvantaged to their peers in their birth year age group. But RAE requirements drastically differ across all state soccer bodies.

In NSW and Northern NSW she would be eligible to play in the under 15s given the biological maturation calculation they use.

In Victoria, South Australia, Western Australia, Queensland and the Northern Territory things seem to focus on individual cases; and in Tasmania there appear to be no guidelines at all.

The ACT has three requirements based on an age group's 50th percentile: you must be born in the last three months of the year, and in the under 15 girls case, must be under 162cms and weigh less than 52kgs.

These guidelines were reviewed last year by the peak body.

Capital Football chief executive Chris Gardiner defended the ACT's requirements but sympathised with the situation.

He said he understood the need and problem of such regulations with the intentions to protect the safety of all players.

"RAE is in place for both fairness (in an NPL setting) and safety. Where a player seeks to play outside their age limit, height and weight criteria are used to consider the request, relying on national averages and percentiles," he said.

"I note that the percentiles used provide significant 'leeway'. Where an exemption is sought, the data can be sent to a decision-maker for independent assessment.

"This year we have had requests for exemptions from two female and 13 male players. Other than this case, the decisions have been unchallenged."

An independent assessment was conducted after the club's technical director and the family requested it, but it was subsequently denied again.

Now Mackenzie has a decision to make, play under 17s or seek another competition.