Nova Scotia revokes teacher certifications at a higher rate than any other English-speaking province.

For every 1,000 Nova Scotia teachers, 4.2 have had certificates revoked, according to data collected for a CBC Marketplace investigation into teacher discipline and transparency.

Both an education expert and the province's own teacher certification registrar say they have difficulty explaining why.

"It's surprising. It certainly does seem to be an outlier," said Robert Bérard, graduate education director at Halifax's Mount Saint Vincent University.

"I don't think there's any reason to believe that teachers in Nova Scotia are more likely to commit offences than teachers anywhere else."

Nova Scotia has the highest rate of revoked teacher licences. (CBC News Graphics)

'Quite puzzling'

Between 2005 and 2015, Nova Scotia voided teaching certifications of 44 teachers.

Only the larger provinces of Ontario and British Columbia voided more.

"The numbers are really quite puzzling to me," Bérard said.

Marketplace collected statistics from every province except Quebec.Education falls under provincial control, which means every province and territory has its own disciplinary process, including for investigations and voiding certificates.

"It would be different from jurisdiction to jurisdiction," said Paul Cantelo, Nova Scotia's teacher certification registrar.

He said Nova Scotia's high number of revocations might be a positive sign.

"It could point to the fact that we could be very, very good with our due diligence here in Nova Scotia," Cantelo said.

Secretive sex-related revocations

A freedom of information request by CBC Nova Scotia showed roughly 70 per cent of Nova Scotia teacher revocations and suspensions between 2000 to 2014 involved offences and allegations that were sexual in nature.

Those included sexual assault, sexual exploitation, sexual impropriety, sexual relationships with students, inappropriate relationships, child luring and child pornography.

The Nova Scotia Department of Education and Early Childhood Development would not reveal the details of the cases, citing provincial privacy legislation.

The department also refused to share details of 18 other cases where action was taken by the registrar, except to say the cases "involved a diverse range of misconduct."

"We face the challenge of balancing public safety while adhering to the protection of privacy legislation that we have in Nova Scotia," Cantelo said.

"Finding that balance between privacy of the individual and protecting the public is incredibly difficult."

In Ontario, the teaching profession regulates and disciplines itself. Details of disciplinary proceedings are made public on the website of the Ontario College of Teachers.