It's enough to make parents blush and wash mouths out with soap. But many have no one to blame but themselves.
Nearly 60 per cent of children swear and 42 per cent pick up bad language by age three, a Daily Telegraph poll in Australia has revealed.
And by kindergarten, more than 90 per cent of children have said a rude word. Despite the overwhelming majority of parents - 78.4 per cent - actively discourage swearing.
Tauranga Region Kindergartens principal Peter Monteith said listening to what adults had to say was how children learned.
"So if they hear a lot of swearing they're going to do it because it's normalised. You don't deal with it by out-lawing it. You deal with it by teaching them how to speak appropriately."<inline type="recurring-inline" id="1003" align="outside" enforce-sites="no" />
Mr Monteith said saying "don't swear" often encouraged young children to keep swearing. He said the answer lay in parents watching what they themselves said around their children.
"What we find with all learning is parents are the key. Parents are children's first teachers and their interaction is greater than TV."
Positive Families family and child therapist, Marjorie Douglas, said she had witnessed parents finding swearing "cute" when children first learned to talk.
Children looked for attention and endorsing swearing was never a good thing, she said.
Ms Douglas said a lot of Kiwis used the "f-word" out of context. "Kiwis in general, especially young male Kiwis, I hear them say it a lot. To certain people it is totally socially acceptable."
While children might be reprimanded at school for swearing, many got away with it at home and it sent mixed messages as to what was okay, she said.
Brookfield School principal Robert Hyndman said swearing at school was unacceptable.
Most primary school children did not use swearing in conversational language. Instead the odd word popped out when they were "emotionally distressed."
"If schools are not proactive in discouraging this, you will have more."
Mr Hyndman said the golden rule at Brookfield School was: "Keep our hands and feet to ourselves and watch what comes out of our mouths."
He believed the evolution of social media was responsible for lowering standards and principal of Pahoia School, Steve Wadsworth, agreed.
He said he'd heard swearing on television before, including primetime news.
"There must be some real hard decision making going on in households around New Zealand. You want children to be educated but when people being interviewed are swearing, that's sad isn't it? "
On the Bay of Plenty Times Facebook page, many parents blamed radio commentators for normalising swearing. Others said their children picked swearing up from their peers.
Leah Stewart said she believed all children went through a swearing phase.
Ms Stewart said she was brought up never to swear in front of her parents, or other adults, and still found it awkward when she accidentally swore in front of her parents. "I teach my son that they are adult words only to be used by adults," she said.
Jo Protzman said she taught her daughter that swear words were "Mummy words".