The most dangerous form of asbestos has been found in three public schools at Engadine and Heathcote.
State Opposition Leader Jodi McKay said students were at risk from the friable asbestos, which is unsealed and crumbles when touched.
The state government denied students were at risk, accusing Labor of "scaremongering".
An Education Department register, established in 2008, records asbestos in more than 1800 public schools in NSW.
During a visit to Heathcote electorate, Ms McKay said friable asbestos had been found in the girls' and boys' toilets at Engadine Public School and Marton Public School, and in at least three buildings at Heathcote High School.
Ms McKay said a further eight schools in the electorate had been identified as having damaged asbestos, which presented a low to medium risk, but had the potential to degrade and become friable.
"Parents deserve transparency from the government," she said.
"The school holidays, starting on September 30, provide an ideal opportunity for the government to either remove asbestos or commit to a timetable for removal."
Ms McKay said Premier Gladys Berejiklian went to the last election promising to eliminate the maintenance backlog at every school by July 2020.
"I hope she truly meant that because there is nothing more urgent than removing dangerous asbestos where it could pose a risk to teachers and children."
Labor upper house MP Mark Buttigieg, who is a party spokesman for the Heathcote electorate, said he was extremely concerned parents weren't being provided with enough information about the asbestos issue.
"It's a pretty basic expectation of government to provide a safe environment for kids in Engadine and Heathcote when they go to school," he said.
A spokeswoman for Education Minister Sarah Mitchell said "children are not at risk and the Labor members are running a scare campaign".
Heathcote MP Lee Evans accused Ms McKay of making "deceitful, hypocritical and irresponsible" statements.
"The Department of Education has a rigorous system in place when it comes to the management of asbestos in schools," he said.
"When there is any suspicion of airborne asbestos, immediate action is undertaken to ensure there is no risk to teachers and students."
Mr Evans said, in most cases, it was safer to leave non-airborne asbestos contained and sealed.
"This is consistent with guidelines administered by NSW Health and SafeWork NSW," he said.
Mr Evans said a Labor government had "done nothing" while in power for 16 years "to mitigate the so called threat of asbestos in schools".
"Asbestos was a commonly used material in most Australian buildings between the 1940s and the 1980s, which is why it is present today in schools, offices, grandstands and even Parliament House," he said.
"When asbestos is properly managed it does not pose a risk to human safety."
