ERO's manager of evaluation services, Stephanie Greaney, said school boards and leaders needed to make sure students were kept safe. That included having robust standards and practices around hiring and monitoring of staff.
"Our findings highlight that although all trustees and school leaders agreed that student safety is paramount, some schools need to increase their commitment to students' safety when employing and managing staff," Mrs Greaney said.
Secondary Principals' Association president Tom Parsons said the report was a timely reminder as school staff readied themselves for the new term.
However, he disagreed that one third of schools were potentially unsafe for students.
Many school staff understood appropriate action and procedures, he said, without those steps necessarily being written down.
While undertaking its review, ERO also became aware about concerns that schools were dismissing staff for misconduct but not informing the Teachers Council, so other schools would be aware of the teacher's history.
Of the schools surveyed, only 48 per cent described the requirements for communicating with parents of a student involved in an investigation, and only 15 per cent described procedures for supporting the student when they returned to school.
Sixty-five per cent of school boards had not provided training for teachers in how to recognise signs of child abuse and respond appropriately, and very few had talked about the potential risks of people "grooming" students.
The speed at which schools investigated complaints against staff was also identified as an issue.
Information for the ERO report included online surveys and scheduled reviews of 173 schools with primary-aged students, and from focused reviews of 27 schools with years 9 to 13 students.
Safety in school
• One third of schools unlikely to react appropriately to situations where students could be at risk from staff, report finds.
• NZ School Trustees Association to remind schools that incidents of serious misconduct must be reported to the Teachers Council.
• Principals' Association says report a timely reminder.