Radioactive rock found at Sydney school

A radioactive rock that was found at a Sydney high school did not pose a danger to students or staff, the education minister says.

Sarah Mitchell was questioned on Tuesday about the radioactive substance that was found at Randwick Girls High in Sydney's east on August 17.

No harm was posed to staff or students at the high school after a science teacher discovered the rock sample in a storeroom, she told a budget estimates hearing.

"There should be no cause for concern or alarm from ... parents," she told the inquiry.

The Australian Nuclear Science and Technology Organisation (ANSTO) was called in to clean the site and collect the hazardous material.

"We have made it clear the independent experts have come in and assessed the situation and have said very clearly that no harm was posed to staff or students, so that needs to be very clearly put on the record," she said.

ANSTO scientists said the sample would have to be held for 250 hours consecutively to have any adverse effects.

Labor MP Courtney Houssos pushed Department Secretary Murat Dizdar to identify the specific radioactive sample but he refused saying he couldn't understand the chemical symbols.

Ms Mitchell accused Labor members of the committee of "scaremongering" adding that it was an "isolated incident".

Ms Houssos then pressed the minister and her staff about proposals to set up retail shops on the site of a high school in southwest Sydney.

"The option for this school is that these high school students won't have an oval but they'll have access to a McDonald's," she said.

The education minister pushed back saying there were no definitive plans for Edmonson Park.

Blueprints from a developer suggesting a "mixed use" building were not final and the department was yet to make any decisions, she said.

"The school infrastructure will consider the options that are available and make decisions in terms of what is the best value for taxpayer money and what is best for the community," Ms Mitchell added.