Middle and secondary schools in B.C. have until September to stop selling unhealthy food in vending machines. (Canadian Press)

Some secondary schools in British Columbia are taking a big financial hit as a result of the no junk-food policy brought in by the provincial government earlier this year, a school board chair says.

Ken Denike, chair of the Vancouver Board of School Trustees, said the new policy has cut down one huge source of "flexible funding" schools have had for sports and music events.

"In some situation, the revenues are down 50 per cent," he told CBC News Friday. "So if it was a large high school raising $70,000 to $80,000 a year they're now raising $30,000 to $35,000 a year."

High-sugar and high-fat foods such as cookies, muffins and fries have been banned since January in elementary schools. Middle and secondary schools will follow in September.

Some secondary schools have already switched over their vending machines to offer milk, granola bars and other healthier choices, Denike said.

Connie Denesiuk, president of the B.C. School Trustees Association, said it's too early to say how schools will be affected because many won't convert to the new rules until September.

A few schools are actually reporting a small increase in revenue, she said.

"What we're looking at is [that] probably the parents along with the staff will come up with some type of plan to meet any shortfall that might be realized," she told CBC News on Friday.

Denesiuk said schools will eventually find ways to adjust to a policy that everyone knew had to be put in place for a healthy lifestyle.

With files from Lesley Pritchard