Secondary school principals say improvements to their schools' finances will be undermined by recent changes in government funding.
Ministry of Education figures show the financial performance of secondary schools has improved in the past three years.
They made a collective surplus of $11 million last year - with fewer recording deficits and more having enough cash and investments to cover their debts.
The Secondary Principals Association says that is because principals and boards have become better at finding sources of income to add to their government funding.
But the association says the improvement will be short-lived now that the Government is docking money when students leave during the year.
Meanwhile, the primary teachers' union, the NZEI, does not expect any respite for its schools, which collectively had a record low surplus last year.