Ontario will offer full-day kindergarten to four- and five-year-olds, beginning with 35,000 children in September 2010, despite a record deficit for the province, Premier Dalton McGuinty announced Tuesday.

In 2011, 50,000 kindergartners will be attending school all day. Once it is fully implemented in 2015, the program will cost $1.5 billion per year.

McGuinty said the move to all-day kindergarten is essential to build a stronger and more productive economy in Ontario.

"Parents everywhere are the same. All we want is for our children to grow up and be the very best that they might be, to achieve their greatest potential," McGuinty told reporters Tuesday.

"In a highly competitive, global knowledge-based economy it's absolutely essential that we invest in the younger generation to ensure that we build a powerful workforce that can compete and win against the best anywhere on this planet."

The Liberal government is going ahead with the program despite last week's projection by Finance Minister Dwight Duncan of a $24.7-billion deficit for this fiscal year. The Conservative opposition says the province cannot afford the program.

Under the plan, a teacher and an early childhood educator will preside over a class of 26 students.

There will also be before- and after-school programs led by early childhood educators. While those programs will not be free, there will be subsidies for families that cannot pay.

"This is a very, very important step for Ontario," said Education Minister Kathleen Wynne. "It's good for kids, it's good for families and it's good for the province."

The government says that about 25 per cent of Ontario schools already have the space to accommodate the program. The first schools to offer the program will be announced early next year.

Ontario's plan follows a similar one in British Columbia, which will offer full-day kindergarten to all five-year-olds by 2011.

Five-year-olds in New Brunswick, Nova Scotia and Quebec attend kindergarten all day, while Quebec, Alberta, Manitoba and Saskatchewan have some programs for four-year-olds.

In June, Charles Pascal, the Ontario government's early learning adviser, issued a report that said children who attend full-day programs prior to Grade 1 fare better academically and socially.

In his report, Pascal put forward a number of recommendations for overhauling early childhood education, including broadening paid parental leave to 400 days, and combining daycare and kindergarten into a single program from 7:30 a.m. to 6 p.m.

With a report from CTV Toronto's Paul Bliss and files from The Canadian Press