Premier Gladys Berejiklian said Cecil Hills Public School's $16 million upgrade is the latest school to benefit from the state government's historic $6.7 billion investment in school infrastructure over four years.
The premier visited the school on Monday with Education Minister Sarah Mitchell and Mulgoa MP Tanya Davies to open 15 new classrooms plus the extension of the existing hall eight months ahead of schedule.
It is one of seven school projects to open early with more than $1 billion of works completed in 2019, including 42 new and upgraded schools.
"As we've shown this year, it's not just about investing historic amounts into building new schools," Ms Berejiklian said.
"We're getting on with the job of turning those dollars into new and upgraded schools for communities right across the state. And it's very pleasing to see students and teachers moving into their new classrooms months ahead of schedule."
Ms Mitchell said the 42 school infrastructure projects have delivered 679 new classrooms and other world-class facilities.
"We will continue to work hard to deliver the very best for our schools, with more than $1.1 billion of infrastructure investment scheduled for next year," she said.
Prestons Public School's $11.5 million upgrade which includes 10 new classrooms plus an extension of the administration area will also be delivered a year ahead of schedule in 2019.