CARPENTERSVILLE – District 300 and its teachers nearly reached a tentative contract agreement Thursday, but the potential deal fell through after the district balked at a union demand to lower elementary school class sizes further.

The momentary breakthrough in negotiations came after the union, LEAD 300, agreed to a modified compensation proposal made by the district earlier this week that includes additional salary increases and concessions on other benefits, representatives from both sides said Friday.

In exchange for the proposal, the union wanted the district to lower elementary class sizes by “two or three students” from the original offer that capped classes at 28 students from kindergarten through second grade and 31 students from third through fifth grades, LEAD 300 President Kolleen Hanetho said.