It has, however, impacted greatly on Mrs Andrew's personal life, her health, and caused unnecessary stress, the letter reads.
"We feel it is imperative that her efforts be recognised and remunerated and, as such, are charging you for her time at a consultant's rate.''
Ms Cuthbert said primary and secondary schools across the country were taking similar extreme action in response to the injustice they were suffering as a result of Novopay's "teething problems''.
"I think every professional understands there is an element of overtime in every job - but to this extent is ridiculous. Nobody should have to work all weekend and late at night because they can't get through the problems with the new system.''
One of the teachers was missing payments going back to July and the school had to take money from its operational fund to relieve that employee's situation, she said.
"People have bills and mortgages to pay - they can't not get paid.
"We are meant to be providing the best quality education we can, not sorting out the Government's internal payment system problems.''
The issue is by no means confined to Wainui School, or to Gisborne.
At the end of last month, Secondary School Principals' Association president Patrick Walsh presented a bill for costs incurred by 32 schools in New Zealand, totalling around $125,000, to Education Secretary Lesley Longstone.
Individual schools' invoices had ranged from $1000 to $20,000, depending on the extent of problems at each school.
"It originally started as a statement to the minister but these problems have been going on for months and months, and schools now have a realistic expectation that schools will be compensated for these extra hours.''
A Ministry of Education spokeswoman acknowledged it had received the invoice from Wainui School.
