This jumped to more than $15 million in the same period when taking into account all age groups. The year 2014 was the most costly with $8.2m paid out, and $7.1m the following year.
A total of 4715 people have been injured in accidents, 1447 of those, or 31 per cent, on a farm.
ACC said the most common injuries included fractures and dislocations, lacerations, concussions and burns.
Its figures showed 14 people died - six in 2014 and eight last year - in an accident involving an ATV.
However, the number of fatalities could be higher, because ACC only captures fatality data where an accidental death claim has been lodged.
The corporation refused to release the ages of the fatalities, citing privacy concerns.
Labour Party transport spokeswoman Sue Moroney said a ban of kids on quad bikes and better regulation of their use was well overdue.
"We know how dangerous they are, particularly on an adult-sized one," she said.
"Someone's got to stand up for the rights of children, there is no reason why any child should be riding a quad bike. How many more deaths do we need?"
Senior lecturer in sociology at Waikato University Maxine Campbell has long advocated for a ban on children on quad bikes.
"I know it's not as simple as saying ban kids ... but keeping kids safe [has] to be the overriding concern."
Campbell called for better legislation around children on quad bikes.
"A lot of those sorts of things, like seatbelts, it wasn't until we regulated that we got a change in behaviour."
However, Green Party transport spokeswoman Julie Anne Genter wasn't sure legislation was the answer. "I think there's a limit to what [legislation can achieve]. Unlike seatbelts in cars, it's a relatively small amount of people using quad bikes."
She called for a wider conversation between Government, experts here and overseas, and those who used quad bikes.
Land Transport Safety manager Brent Johnston said the transport agency was always looking at how it could make roads safer.
"Any death on our roads is one too many and has a devastating effect on families, friends and communities."
However, it said the use of ATVs on private land was outside its reach.
He said of all the ATV accidents on the road from 2010 to 2015, none involved a child younger than 10.
WorkSafe NZ said quad bike injuries were preventable and recommended that all those who drove one had the right training and experience; that the right vehicle was chosen for the setting; that a helmet was always worn; and that kids shouldn't be allowed to ride on adult-sized quad bikes.
Quad casualties
• 256 Children injured riding all-terrain vehicles - quads, bikes, three wheelers - in last two years.
• 98 Aged 4 and under.
• $36,202 Amount spent by ACC on accident victims under 9 last year.