Community Unit District 300 and the Dist. 300 teachers union have requested a third-party mediator to step in to assist with contract negotiations.
The school board announced the request Thursday afternoon, and said the request was made jointly between the district and the teachers union, known as LEAD300.
The mediation request was necessary because of state law passed last year that requires a neutral third party to assist in the negotiations if the parties haven't agreed on a contract by a certain date before the first day of school.
The two sides agreed to a one-year agreement in the spring of 2011, but that agreement expired on July 1.
The school board and LEAD300 began contract talks in January with the hopes of agreeing to a multiyear contract.
According to the school board, LEAD300 is asking for "substantially" lower class sizes, but has not presented a specific proposal with a salary schedule and benefits.
The school board argues that pension reforms, which have been a hot topic in Springfield, are "inevitable" and that the reforms will push pension costs onto school districts. The Illinois Senate has approved legislation that would cut back annual pension benefit increases for state workers, but teachers were not included.
The House may take a vote on the measure in August, which would not shift future pension costs of teachers from the state to local schools, although the idea is backed by some legislators.