The new Education (School Donations) Bill going through Parliament is "significantly inequitable", National's education spokesperson Nikki Kaye says.
The Government's Budget included more than $75 million a year to pay $150 per child in donations to every decile 1-7 school.
Ms Kaye told TVNZ1's Breakfast she thinks it's unfair that deciles 8, 9 and 10 aren't included - with parents still asked to pay school donations.
"There's a whole number of schools that are 8, 9 and 10 that has disadvantaged children so they've got some significant inequity," she says.
Since 2000, parents have shelled out $1 billion in so-called voluntary donations in primary and secondary schools throughout New Zealand.
Ms Kaye believes there are two options, the first being, scrap the decile system.
"We believe in more funding for schools. There clearly has to be more funding so that parents pay less, the question is how you do that?" Ms Kaye says.
She says scrapping the decile system would see better distribution of funding for all schools.
"The other option is we argue to extend the scheme to 8, 9 and 10."
At midnight last night submissions closed on the bill and Ms Kaye says she believes a lot of parents and schools are not having their chance to be heard.
"There's hundreds of thousands of parents that would have a view on this and I'm concerned they will not have that opportunity."