The state's most neglected school, according to the value of maintenance and repairs required, was for the second year running Great Lakes College in Forster, which needs $3,328,868 worth of work done.

It was followed by Marsden High School in Ryde, with a maintenance backlog of $2,882,626.

Others among the most in need of work include the selective Sydney Boys High School in Moore Park and two primary schools in Epping, Epping West and Epping Public.

In 2014-15, maintenance and repairs worth $732 million sat on the state's books - an increase of 36 per cent on the previous year.

The new data, obtained by the Opposition under the Government Information (Public Access) Act, shows there is now $775 million worth of work that has been logged but not done.

And the number of neglected schools waiting on more than $1 million worth of work has grown from 120 to 147 of the state's 2181 government schools, as at June 30.

The most common works requested were toilet and sewer upgrades, leaking roof repairs, carpet replacement, painting, guttering and replacing broken windows.

This is despite the department budgeting $342 million for maintenance in schools in 2015-16, of which $80 million was supposed to address the backlog.

Several schools remain on the state's neediest list for the second year running, including Great Lakes, Marsden, Tamworth High School, Colo High School and Northmead Creative and Performing Arts High School.

Opposition Leader Luke Foley said: "Under the Baird government, schools are falling apart and our state's children have been left to learn in schools where broken toilets, busted windows and worn carpet are considered perfectly acceptable.

"Mr Baird is the first person to big-note the NSW economy but he won't open the cheque book to start funding the repair of our state's classrooms."

Individual principals are not permitted by the department to speak to the media.

A department spokesman said a boost to the maintenance allocation in the 2016-17 state budget, the largest in 20 years, was in addition to the ongoing maintenance program and would help address the problem.

"In the 2016/17 state budget, an extra $330 million was allocated over the next two years to allow for planned and priority maintenance works to be undertaken in schools across the state," the spokesman said.

"This increase in funding will target roofs, floor coverings and painting, as well as other backlog maintenance works selected by school principals. The department is currently consulting with principals to plan these works to ensure high priority maintenance items are undertaken first.

"Over the next two years it is expected that $5.9 million will be spent in the Myall Lakes electorate and $2.30 million in the Ryde electorate on planned and priority maintenance."