Hudak, who supported the roll out of all-day learning for four and five-year-olds before the 2011 election, said the province can't afford the program, which would cost $1.5 billion a year when fully implemented.
It's not a question of whether this is good program or a bad program, Hudak said.
"It's what can you afford, and when you're staring at that type of a hole you need to make some difficult decisions now."
Full-day kindergarten is currently available to about 120,000 students in more than 1,700 of the 4,000 elementary schools in Ontario, but the Opposition leader wasn't worried about creating a system of have and have-nots by making the rest wait until the deficit is eliminated in five years.
"Difficult decisions are the necessity of leadership when you’re staring at a huge deficit," said Hudak as he released a white paper on education reforms.
"There are areas we need to give greater emphasis, raising the bar when it comes to basics like math and literacy, to give a hand up to those under performing schools where we condemned kids with half of them failing their basic skill levels."
Education Minister Laurel Broten lashed out at Hudak for repeatedly changing his position on full-day kindergarten, and said Ontario can't afford not to fund the program.
"We need to invest in our youngest learners because it’s investing in the future of our province," Broten said in an interview.
"Tim Hudak has had every possible position on full day kindergarten ... originally against it and calling it a frill, supporting it when polls showed it was popular, and now I think his true colours are coming out."
The New Democrats also accused Hudak of having the wrong priorities.
"Tim Hudak thinks that people earning $500,000 a year need an immediate tax cut, but parents who need full-day kindergarten should lose their programs," said NDP education critic Peter Tabuns.
"Parents and kids want peace and stability in our classrooms."
The Tories also want to review the all-day learning program to see if a teacher and an early childhood educator are needed in both Junior and Senior kindergarten classes, which Broten said was the proper model for the program.
Over the past decade Ontario increased funding for education by $8.5 billion a year even though there are 250,000 fewer students, complained Hudak.
"That's neither acceptable nor sustainable when we're faced with a $12 billion deficit," he said.
The Conservatives' white paper called for the elimination of 10,000 non-teaching positions from school boards, but Hudak said he wouldn't want to eliminate educational assistants for special needs students.
That shows a lack of understanding of how the system works, said Broten, who defended the need for non-teaching staff at schools.
"They’re educational assistants who work with our children with special needs, they’re librarians, they're custodians who keep our schools clean and safe, they’re children’s mental health workers," she said.
"I find it very disconcerting that Mr. Hudak would think their roles are not important."
Hudak also wants to eliminate school superintendents and give principals more powers, including the ability to reward teachers who outperform their colleagues and go above and beyond with their students.