Education Review Office chief executive Nicholas Pole wants more support for children facing a stand-down or exclusion from school.
Appearing before the Royal Commission on Abuse in Care, Pole said families needed help navigating schools' disciplinary processes.
"My own view is there should be greater protections and greater advocacy and support for whānau going through the process of having their child stood-down or excluded."
Too many children who were excluded from a school were being enrolled with correspondence school Te Kura instead of being re-enrolled with another regular school, Pole said.
High levels of exclusion and stand-downs were often linked to poor practices in schools, he said.
"Often it is a manifestation of the quality of teaching, the quality of leadership, the quality of governance, practices and systems in the school and a lack of that collective teacher efficacy where teachers are working together to make sure every single learner is successful."
Schools' cultural competence varied greatly and only about 10 percent of schools fulfilled their obligations under the Treaty of Waitangi, Pole said.
"We see some schools who do this well, that's not the majority. So at the moment in terms of our assessment and our assessment with respect to responsiveness to Te Tiriti, only about 10 percent of schools we are working with we would say are reflecting their obligations to the fullest extent at present."
The number one focus of the review office (ERO) was support for Māori children, Pole said.
ERO had previously reported bullying was a serious problem in schools, he said.
Anti-bullying initiatives could reduce the level of bullying but did not eradicate it altogether because it was a wider societal problem, he said.
"There is something about New Zealanders and you only have to be on the side of a nine-year-old's soccer field in even affluent areas, having been a soccer coach for many years, where parents' behaviour on the sideline is atrocious and this is played into our schools. I think it's something we need a national conversation about."
The commission should consider whether it should be mandatory for teachers to report any cases of suspected abuse, Pole said.
Counsel assisting the commission Tania Sharkey asked Pole and ERO officials about the extent of their power over private schools and their boarding facilities.
Pole said there had been cases where the values of private schools and of the parents who sent their children to those schools did not support children's wellbeing.
He and other ERO officials were questioned about an unidentified school which received negative review reports for a period of 14 years starting in 1995 but had no recent review report.
They said the office was still working with the school and a report was being prepared.
They said the office had raised fears for students' health and safety with the school's board, but the board had not agreed.