A third of schools are unlikely to recognise teachers who could pose a risk to pupils, the Education Review Office (ERO) says.
It reviewed schools' practices for appointing and managing staff at the request of the State Services Commission and the Ministry of Education after two recent inquiries into the employment of sex offenders.
Two-thirds of schools reviewed had satisfactory practices for appointing and managing staff which were designed to keep students safe.
"However, the practices of one-third of schools meant they were unlikely to recognise situations when students could be at risk from staff and respond appropriately," ERO said.
"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," ERO manager evaluation services Stephanie Greaney said.
"In addition, education agencies need to actively support schools by making sure advice and regulation about what is required is easy for school trustees to find and understand," she said.
The report included recommendations for schools and education agencies, along with questions which boards could use to review and improve their own employment practices.
A third of schools ERO investigated had "robust" practices and closely followed procedures that focused on child advocacy when appointing and managing staff. The report included examples of those practices, and information about resources boards could use when employing staff.
The evaluation was completed last year, with information gathered from online surveys completed by principals and boards of trustees' chairpersons, from scheduled reviews of 173 schools with primary age students, and from focused reviews of 27 schools with years 9 to 13 students.