Every state school classroom in Queensland would be air-conditioned under a Liberal National Party plan.
The "cool schools" plan was part of Opposition leader Deb Frecklington's budget reply speech on Thursday in which she outlined the LNP's alternate plan for Queensland's economy.
"We air-condition our hospitals, our prisons and our parliament but we let our kids swelter," Ms Frecklington said.
"We want our kids to be the smartest in the nation ... as well as the coolest."
However the Labor government has seized on comments back in 2014 by former LNP education minister John Paul Langbroek, who said the scheme would not be feasible as it would cost around $2 billion.
"I'm looking forward to seeing where the opposition leader is going to find $2 billion a year, let alone the $50 million a year in electricity costs," Premier Annastacia Palaszczuk told reporters on Thursday.
She said the Labor government had been working to put air-conditioning into schools in the far north and west of the state which need it most, as well as providing solar panels to bring down the cost of running the units.
Temperatures in regional Queensland frequently top 40C in the summer months, including at the start and end of the year when schools are still in session.