Fewer students will have to swelter through summer, with the New South Wales Government spending $500 million to put air conditioning in up to 1,000 schools across the state over the next five years.

The budget announcement steals the Opposition's thunder — it planned to spend $300 million boosting air conditioning in schools.

The Government said classrooms and libraries in every new and upgraded school will now be air conditioned.

The criteria for retro-fitting older schools will be changed to include factors like humidity and classroom design.

Premier Gladys Berejiklian said: "this funding will ensure thousands of classrooms that previously did not have air conditioning will now receive it".

"This is something that parents and school communities have called for and we are the only government that can deliver this," Ms Berejiklian said.

However, Opposition Education spokesman, Jihad Dib, said over the summer the Government resisted repeated calls to boost air conditioning.

"Ironically the Government was very dismissive of Labor's air conditioning policy and it seems now they've decided to copy it," Mr Dib said.

"I think in many ways it makes me pretty proud because the Government doesn't have the courage to put policy ideas out there.

"They've just waited to see what the reaction is and when they've worked out it's a really important policy, then they've followed suit."

Coping with 44,000 more students

Next week's budget will also contain $6 billion over the next four years to build new schools and upgrade existing ones, as the Government tries to keep up with soaring student enrolments.

The money will be spent on 170 schools, with planning work to start on 20 this year.

New primary schools will be built at Green Square, Westmead, Edmondson Park, Gregory Hills and Rhodes East in Sydney, as well as Murrumbateman near Canberra.

There will also be a new high school at Edmonson Park, as well as upgrades to Birrong Boys High, Birrong Girls High, Randwick Boys High, Randwick Girls High and Cecil Hills High.

The Government said 2,000 new classrooms will cater for nearly 44,000 more students.

Mr Dib welcomed the cash injection, but said there were still areas crying out for new schools.

"Have a look at somewhere like the Ponds High School for example, built four years ago but it's already above capacity," he said..