Some schools organising their own bus services do not know its up to them to monitor safety standards.
In 2019 Auckland company Kiwi Coaches was found to have been running a dozen school buses that weren't roadworthy, including some that had brakes that did not work properly.
It was only when RNZ contacted the schools which used the company that they had any idea Kiwi Coaches had been under investigation by Waka Kotahi NZ Transport Agency.
New Zealand Principals' Federation president Perry Rush said that was unacceptable.
"We absolutely would expect a bus company to have a duty of care to their customers and in this instance those customers are children, their families and schools.
"There should be really clear disclosure of any issue affecting safety of the service they provide. That would be a basic expectation."
The Ministry of Education spends just over $200 million a year transporting students to and from school.
Operators it contracts are audited every year and if they are being investigated by NZTA or police, the ministry is notified.
Likewise Auckland Transport confirmed it would be told if any school bus companies it contracted were under investigation.
But NZTA does not tell schools which organise their own services - of which there are about 200 - if an operator is under scrutiny.
Bus and Coach Association acting chief executive Alex Voutratzis said it was a dangerous gap.
"At the end of the day we are dealing with children and children's safety needs to be the first priority. We don't tolerate any kind of situation where people want to skirt around that."
He suggested a contract all schools could have access to.
"For example a template provided by the Ministry of Education that listed all the clauses, including disclosure.
"That would hopefully close the loop in terms of responsibility in sharing that information."
Perry Rush agreed.
"Because these schools, the parents in some cases, have organised these services directly with the companies it would make sense if there was some support from the Ministry of Education.
But the Ministry of Education said something like that already existed.
Head of Education Infrastructure Service Kim Shannon said for schools funded to manage services themselves the agreements set out in the legislation was that these schools were responsible for monitoring the safety standards of their transport providers.
"The contract and funding agreement that schools signed at the time outlined their obligations. The contract lists our regional Transport Contract Managers in case schools have any contract or transport-related questions.
"We also make our commercial contract templates available to schools to support them with their due diligence of transport providers," she said.
The contract contained a section called "Sharing of information" which included a provision for the contractor to agree to the access and sharing of information held by NZTA.
Road safety advocate Clive Matthew-Wilson said using that contract would certainly help close the loop, but said more could be done.
"The New Zealand Transport Agency should be absolutely and immediately required to notify everybody that's responsible for bus contracts with that firm.
"It's an absolute no-brainer."
NZTA said it had oversight of a transport service licence holder's ability to operate legally and safely, not the commercial contracts these operators had with their clients.
Schools involved with Kiwi Coaches approached by RNZ declined to be interviewed.