The Illinois Supreme Court heard arguments Tuesday from a man who earned a state teacher pension after substitute teaching --  for one day. 

Contract negotiations between the Champaign Unit 4 school district and its teachers union have stalled. The Champaign Federation of Teachers requested a federal mediator to intervene in the bargaining process, and the district has agreed.

When school districts outside of Chicago negotiate contracts, they do so with the assurance that the state will pick up the tab on pensions. To control growing pension costs, lawmakers capped salary bumps at 6 percent in 2005. This year, the cap tightened to 3 percent. Illinois' teachers unions have collected more than 15,000 signatures on petitions urging state lawmakers to reverse that measure.