"We just have to be very mindful of how we're spending money. We have not reduced any of the services that we have in terms of children -- the board made the decision we would just fundraise more."
The Government allocates schools' funding based on decile ratings, calculated by factors including the make-up of the roll and the wealth of the school's community. Schools with lower deciles receive more funding.
The bulk of decile funding comes under the banner of Targeted Funding for Educational Achievement (TFEA). Decile one schools receive a maximum of $905.81 per student, while decile 10 schools receive no TFEA funding.
Ms Devenport said the Masterton school's fundraising committee have put their creative hats on, holding sausage sizzles, movie nights and a Christmas gala to plug the funding gap.
The situation has been made especially difficult by a 10 per cent rise in the school's roll since 2013 -- almost the equivalent of another full classroom.
Ms Devenport said this has left no room for extras: "It's hard. We have to cover what we need to cover and nothing more."
Deciles are recalculated after the census every five years. But with the 2011 census being delayed two years after the Christchurch earthquake, schools that felt they were under-funded were doing it tough for a long time, according to the chairman of the New Zealand Secondary Principals Council, Allan Vester.
"I know a lot of schools would complain they've lost money -- the other way of looking at it is schools that have gone down in decile really should have had the additional money earlier," Mr Vester said. "If you were one of these schools, there would be a number of years where you were under-funded according to the real decile."
He said funding cuts seldom affected teacher numbers but often hit administration staff and extracurricular activities.
Some schools ask for higher donations from parents or fundraise, like Fernridge School, while others look to cut maintenance and administration costs.
Education Minister Hekia Parata has called the decile system complicated and clumsy, and is looking at how school funding can be improved. She said a review was in its early stages and decisions were "still some way off".
Ms Devenport agreed the system needed to be looked at. "Funding schools is a tricky situation, and nothing works completely, so it's hard work. But that's a Government issue, not my issue. We've been given what we need ... You've just got to make it work."