TORONTO - Ontario can't say how many schools will close under proposed cuts announced in this week's budget, or which areas may be most deeply affected.

Education Minister Laurel Broten says the government is committed to ending subsidies for underused schools, but it will be up to school boards to decide which ones to shut down.

She says using school buildings effectively requires "an extensive conversation" and it's not up to Queen's Park to make that call.

The province said in its budget Tuesday that class sizes will remain the same but some underutilized schools will be closed and boards will be amalgamated in sparsely populated areas.

The change, starting in 2013-14, is expected to create annual savings of $70 million.

New Democrat Peter Tabuns says the move is worrisome because demographics can quickly change and more kids could end up having to be bused to schools far from their homes.