"The ministry are still getting paid, the tertiary people are still getting paid but not the schools and that's all the caretakers, the teachers, administration, and everything paid through the school system."
Ms Forrest said school staff most affected are the mixed income, part-time and ancillary staff, teacher aides and administration workers.
"I feel relatively fortunate because I don't have a family to support. But I know colleagues with families that are in deep strife financially and principals who are working huge hours trying to do payroll's job," she said.
Gladstone school principal Margaret Hyslop said she had been battling persistent pay problems, including "someone on the payroll I don't employ" since the system launched in August.
Some problems had been resolved but other flaws continued despite Novopay, run by Ministry of Education payroll provider Talent2, now reaching its fifth pay cycle.
After payment faults during the first pay cycle, Mrs Hyslop contacted Talent2 and was told she was the 1117th caller in the complaints queue.
"There has been a lot of problems.
"The phone system has been improved but each mistake takes at least an hour to resolve," Mrs Hyslop said.
"That's from five to 14 hours a week to correct and that's over and above normal hours, which is time away from teaching and learning programmes," she said.
"It's a nightmare and an incredibly frustrating system. I hope they get it right by the end of the year but I don't hold out much hope."
A ministry training roadshow for the Novopay system also will be running at Masterton Intermediate School on Monday.
Schools were sent notice of the roadshows last Sunday and event confirmations have been last-minute, says Kevin Bunker New Zealand Post Primary teachers Association general secretary.
He criticised the ministry for its "appalling lack of timing" regarding the roadshow and said compensation should be paid to principals and school staff who spend on resolving payroll faults.
Mrs Mahuta made the same call in Parliament this week for Talent2 to compensate schools.
During question time, it was revealed that in the previous fortnight the number of Novopay errors had leapt from 490 to 3227.