The Principals' Federation says it is time to reveal the details of a technical review held into Novopay.
The $30 million school payroll system developed by Australian company Talent2 has been plagued with thousands of errors since it was introduced in August 2012 with underpayments, overpayments or no payments at all to some teaching staff.
The Government has brought in Deloitte to conduct the technical audit of the stability of the system and the data within it to see whether the software problems can be fixed in the longer term, or if the system is so compromised a replacement will need to be sought.
Wednesday was the 23rd pay cycle under Novopay and Ministry of Education staff received more than 260 calls from school staff reporting problems.
The principal of Beaconsfield School in Timaru, Wayne Facer, says some principals have had to pay underpaid staff out of their own pocket and other schools have had to withdraw money from school credits cards.
The Principals' Federation will meet acting Secretary of Education Peter Hughes and other senior officials on Thursday afternoon to discuss the problems and the technical review.
Federation president Philip Harding says they want all the details of what is and is not being investigated and will need full disclosure of any findings to regain their trust.
The review is expected to be completed in three to four weeks. The minister responsible for Novopay, Steven Joyce, has also ordered a ministerial inquiry.