The Ministry of Education (MoE) says under current rules a case like that of child rapist Robert Burrett couldn't happen again.
The Christchurch school caretaker's been jailed for nearly 20 years for sex offences against girls between 2013 and 2015.
Complaints were made before then but the Ministry says they weren't in relation to sex abuse.
Spokesperson Katrina Casey says rules are now tougher but they'll be investigating any failures there may have been.
"The situation has changed since the 1980s, 1990s and there is greater awareness. One thing to note here, no school or the ministry, or anybody else ever actually received a complaint for sexual abuse."
Newshub.
