Inside a Toronto elementary school, almost every student spends their day playing, learning how to spell and count.

The school, located in the densely populated Thorncliffe Park neighbourhood, is one of North America's largest all-day kindergarten facilities.

The Fraser Mustard Early Learning Academy opened its doors in 2013. This year, approximately 680 four- and five-year-old students fill the school’s 24 classrooms. They are all enrolled in full-day kindergarten.

"We learn how to be good," one young student told CTV Toronto.

She is one of approximately 28 students in her class – the average class size at the Toronto school. Across the province, that number is higher. Many classrooms this year are bulging at the seams, with as many as 40 students in a room. And that will likely not change anytime soon.

Although there is a class size cap for primary grades in Ontario, there is no limit for kindergarten classes. Some parents say they are worried this will affect their child's learning potential.

"I think 20 or 22, not more than that," a mother of a student said. "They are small kids. They need the attention."

But some educators are downplaying the potential effect that bulging class sizes can have on how well some students learn, saying 30 is a manageable number.

"Certainly 30 is not hard to manage. Thirty-four isn’t hard to manage,"Fraser Mustard principle Catherine Ure said. She said many kindergarten classes are taught not only by a full-time teacher, but an early-childhood educator and volunteers.

The Ontario government began rolling out full-day kindergarten learning in 2009, when then education minister and now-Premier Kathleen Wynne introduced the bill for the program.

Over the past five years, the program has been rolled in through phases. The last phase was rolled out this past week. The government has spent approximately $1.5 billion to retrofit and expand schools, on top of millions more in operating costs.

With a report from CTV Toronto’s Naomi Parness