April may be the last month filled with contract negotiations between school officials and the local teachers union, according to both parties. The contract between the union and the town expired on Aug. 31, and there have been months of mediation sessions and educators waging a picketing campaign outside school and town buildings. Stacy Scott, the district’s superintendent, said the two sides have reached agreements on issues such as a cost-of-living pay increase linked to inflation, language that defines the teaching workday, and limiting class sizes. Framingham Teachers Association president Sam Miskin agreed, while noting that they are still working on the contract’s language in some areas. Both Miskin and Scott said they hope negotiations would end after the next scheduled mediation session, which is slated for April 8.