A new report says our math teaching methods are not adding up.

The C.D. Howe institute said math scores across the country have declined between 2003 and 2012. The steepest drop occurred in Manitoba.

The report cited Canada's performance on the OECD's Program of International Student Assessment (PISA) as evidence that a fundamental shift in math instruction may be necessary.

The report blames the decline on discovery-based learning - a method introduced in the late 1990s where students do more independent work using pictures, drawings and objects to solve problems.

“What we are seeing in schools is a lot of things like multiple strategies and convoluted methods and what happens is that children's working memory gets overloaded and they are unable to learn the information properly,” said report author Anna Stokke.

Instead, Stokke said 80 per cent of learning math should be traditional: adding, subtracting, and memorizing times tables, with direct instructions from a teacher.

Stokke said in 2013 Manitoba began reintroducing times tables, column addition and long division.

Manitoba’s Education Minister said the province is waiting on the results from recent tests since the changes were implemented.

- with files from The Canadian Press