Principal Neil Robinson said their aim was to maintain funding support - which over the past few years allowed the school to heat the school pool and build three new playgrounds - but lighten the load on the small group of parents on the PTA.
"What we've found over the last couple of years is that the ability of parents to commit time to fundraising events is getting less and less," Mr Robinson said. "It's not that they're lazy and don't care but in lots of families both parents work.
"For example, we have a lot of families where grandparents are the ones picking kids up from school."
Mr Robinson said most of the feedback so far had been positive, although there would always be those who disagreed.
Parents the Herald spoke to supported the policy.
Kyb Sweetman, mother of 9-year-old student Lucia Sweetman, said she was a regular at many of the school's fundraising events as she worked part-time and had the time to attend.
She also enjoyed helping out at fundraisers, she said.
"I don't mind the changes, I think $40 is okay. But I go to a lot of the events just because I like to help. My older daughter used to go to this school too and I think it's good to help the community that way."
Antonios Gossen said he too was happy to contribute extra towards the school.
"It's good so people who can't come or don't have the time can still help."
Shironi Weerappuliga, who has a 10-year-old at the school, said: "I normally like helping at the fundraisers. I like to helping the school that way. The donation is good too, because it's helping our kids."
One parent, who wished to remain anonymous, said they would not pay the extra fees.
Plimmerton School PTA chairman, Frank Simmons, said the Wellington school was another where parents were offered the option to give a donation instead of helping out.
"Fundraising is a lot of hard work. And there are some parents who make a huge effort and some parents who don't," Mr Simmons said.
High schools are also offering the cash option.
Epsom Girls Grammar ask for a $30 donation each year, which is put towards prizes and school amenities.
The school had separate groups for activity fundraising.
PTA chairwoman Lynley Sheweiry said it was "refreshing" to only have to support school and staff, as fundraising was difficult.
"In my experience we tend to have much larger support at primary school level than at intermediate where, for various reasons, the level of support substantially declines. For example, some mums go back to work, plus children want to be more independent so their parents are not at school as much, just drop kids off or they walk to school."
Minster of Education Hekia Parata said everyone needed to be more creative about how they helped schools. It wasn't always about money, she said. "For example if you're an accountant you could do the books."
