EDUCATION Minister Grace Portolesi has been accused by the State Opposition as being incompetent and overseeing a department with a "culture of cover-ups".

The call comes after Premier Jay Weatherill revealed he first learnt on Friday of two more cases where sexual incidents involving students had been kept secret from parents.

Ms Portolesi had known about the cases for months after a recently-established Government taskforce, which is auditing how historical cases such as these have been reported to parents, began looking into the incidents.

"I think we have a situation where there is a culture of cover-ups within the department and incompetence by the Education Minister," Opposition education spokesman David Pisoni said yesterday.

"There's no doubt that under the current environment, you would expect the minute that Minister Portolesi was made aware of a rape in a school that she would raise that with the Premier, considering he was the education minister at the time of the rape in the western suburbs school."

Mr Pisoni wants the taskforce to be taken over by the inquiry looking into one of the cases, headed by former Supreme Court Justice Bruce Debelle.

"What we're saying is that the duties of that taskforce now must be handed over to Mr Debelle," he said.

"Only then can we be confident that it will be an independent and thorough inquiry."

But Mr Weatherill yesterday defended Ms Portolesi and the Government's handling of the issue.

"The Minister for Education has been working with a taskforce that has been established to put in place an audit of all of the circumstances that have occurred historically in relation to the reporting of child sexual abuse in schools," he said.

"The process that's gone on here is that we have reviewed past cases.

"There was a certain set of advice coming to the minister during the period some months ago; that advice has now changed given the nature of the controversy of the parents not being informed, so everything is being reviewed.

"People are methodically working through those past cases to work out whether and how parents should be told."