For many Kiwis, watching their children play sports is a delightful rite of passage.
But some parents take their passion too far - abusing referees, the young players and clashing with other parents.
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One man was charged with assault after breaking a volunteer ref's jaw in three places.
Next month, the South Canterbury Rugby Union will install sideline spies who will covertly observe games, and be able to 'red card' parents whose enthusiasm gets the best of them. They could be at any game for any age range.
South Canterbury Rugby chief executive Craig Calder told The Project that he's seen a lot of anti-social behaviour toward the teenagers who referee kids' games.
"They're out there, getting up early and giving up their time, and what are they getting? A bit of sledging. Not nice sledging - some of it's pretty heavy-handed sledging."
He says the comments, many of which target the ref's ethnicity or sporting ability, can have huge impacts on the young people being targeted.
"We've seen trends throughout New Zealand that kids give it up after a year. They try refereeing, get abused and we don't see them back the next year."
The so-called spies will be armed with lollipops, which they can present to angry parents with a single line: "Suck on that."
"It really is the responsibility of the parents and the supporters to put the lolly in the mouth and be quiet," says Mr Calder.
He says while the ref technically has the power to remove overzealous spectators from the park, they don't want to have to resort to that.
"We just want people to have a look at themselves and just see and hear what they're saying to these kids," he says.
"Keep it simple, keep it sweet on the sidelines."
Watch the full segment on The Project.
Newshub.