The state government said the funding would result in more than 60 facilities being either built or upgraded in Sydney's west and southwest over the next four years.
Premier Chris Minns said the money would be a "game-changer" for the burgeoning areas, where some suburbs had gained up to 8000 residents without a new school being built.
When asked what would be cut from the budget to allow for the education blitz, he told reporters that difficult fiscal decisions "did not extend to the education of the next generation of young Australians".
The state's treasurer has flagged a tough budget, which will also need to incorporate funding for a significant one-year increase in teacher pay.
Education Minister Prue Car said the school infrastructure funding would be "life-changing" in areas popular with young families, adding that it built on the wage deal for public school teachers.
The union-agreed package includes a more than 12 per cent pay increase for entry-level teachers as part of an attempt to address chronic staff shortages in classrooms.
"This government has moved historically to restore teachers' wages to where they should have always been," Ms Car said.
The infrastructure funding would give Sydney's west quality public schools, while the coalition in government had failed to support the growing communities, she added.
But opposition education spokeswoman Sarah Mitchell said nine of the 15 additional schools announced by Labor were already funded under the previous government.
"We invested more than any other government in the history of NSW in school infrastructure so for them to claim that no work was done is untrue," she told AAP.
The government said new primary schools would be located near Sydney Olympic Park, Gables, Melonba, Tallawong, Gregory Hills, Nirimba Fields and Liverpool.
New high schools will be situated at Wentworth Point, Melrose Park, Melonba, Schofields and Tallawong, Jordan Springs, Gledswood Hills and Gregory Hills, Leppington and Denham Court, and Edmondson Park.
The multi-billion dollar promise comes despite the government being under pressure to curb spending after admitting it faced about $7 billion in budget pain-points in the next four years.
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