More than 100 Celina City Schools teachers and supporters on Monday afternoon march on Wayne Street from the primary school to the Mercer County Courthouse. "This is a show of unity and teacher support for our negotiating team on the day that contracts expire," Celina Education Association co-president Dave Scott said. The two-year contract for the approximately 198 teachers expired Monday. Negotiations on a new pact began July 24 and a federal mediator was requested after two days of bargaining. A session with the mediator was held Aug. 21 and the next is scheduled for Thursday.