SPRINGFIELD – Illinois schools could see costs rise by nearly $600 million after five years of a plan to make them shoulder the expense of providing pensions for teachers, according to new figures meant to support Gov. Pat Quinn’s argument for shifting some state retirement costs to school districts.

But critics remained dubious Tuesday. They said that amount – a small percentage of overall education spending – could still force many districts to cut programs and staff or raise local taxes. They also questioned whether reliable estimates are possible with such a complex, changing issue.

“I don’t have any confidence in the upper end of those numbers,” said Michael Chamness, a spokesman for the Illinois Association of School Administrators.