The Education Ministry accepts it failed to adequately monitor schools' practice of shutting children in seclusion rooms before it was banned in 2016.
Senior leaders from the ministry appeared before the Royal Commission Inquiry into Abuse in Care today.
They acknowledged past failures by the former Education Department, including a failure to support the use of te reo and matauranga Māori.
Secretary for Education Iona Holsted told the commission the ministry could not assure children's safety on a day-to-day basis because it did not have direct daily oversight of schools.
For the same reason, it could not guarantee that schools were no longer using seclusion - shutting a child in a room, she said.
The ministry relied on good systems and on good people working in and with schools to ensure they did not break the law, Holsted said.
"A devolved system by its nature relies on an element of trust. We simply don't have a system where we could have everybody monitoring everything all the time," she said.
Holsted said she had no reason to believe there were current reports of abuse in schools the ministry was not aware of but she could not rule it out.
There were more points to which abuse might be reported than in the past, such as the Education Review Office (ERO), but most parents would contact the ministry if they had a complaint about their school, she said.
The former Department of Education had less oversight of private schools than of state and state integrated schools and that might have provided opportunities for predators, she said.
The department also breached the Treaty of Waitangi by failing to support te reo and matauranga Māori, she said.
"I acknowledge that the Department of Education failed to actively protect te reo and encourage its use by iwi and Māori and that was in breach of Te Tiriti o Waitangi and this has had an ongoing detrimental effect on the acquisition and the use of the Māori language," she said.
Consistently lower expectations for Māori students and other groups had harmed their achievement, Holsted said.
Unconscious bias could be devastating and the ministry was trying to reduce racism and ableism in schools, she said.
Counsel assisting the commission Michael Thomas read from statements from people who said in the 1960s and 1970s their education was curtailed because they were in state care, they were prevented from using Sign Language while at a school for the deaf, and were sent to a boarding school for the blind at a very young age.
Holsted said "without a doubt", there was still more work to be done to make schools more inclusive of students with a disability.
"ERO is very positive about the quality of our inclusive curriculum and the resources we produce to support teachers, however, we also know that the majority of teachers are not using them," she said.
She wasn't blaming teachers because they were busy and needed support to make use of new material, Holsted said.
Under questioning from counsel Katherine Anderson, Holsted said in hindsight knowing now about the level of abuse in Catholic private schools in the 1970s, the government should not have extended funding to those schools.
The ministry would try to help any school with a disproportionately high exclusion and stand-down rates for Māori and Pacific students, she said.
Changing a school required good leadership and teachers who could work well with a range of students, Holsted said.
"Some of the behavioural challenges that are facing teachers now that weren't necessarily there 10 years ago, even five years ago are testing," she said.
The ministry had been too slow to act on reports of problems at schools in the past and it would not make that mistake again, Holsted said.
The commission was scheduled to hear from the Education Review Office and the Teaching Council on Friday.