ANDOVER, Mass. (AP) — Andover Public Schools were closed Monday as hundreds of teachers remained on strike for a fourth day after the Andover School Committee and the Andover Education Association, which represents teachers, failed to agree on a new contract in bargaining sessions over the weekend.

Classes have been canceled for the district’s roughly 5,500 students in prekindergarten through 12th grade since a Thursday night vote by the Andover Education Association to go on strike.

The parties were scheduled to resume negotiations Monday.

The school committee said it could not agree to a union proposal of an 18% raise over four years for all teachers without the town overriding Proposition 2½ at a townwide election to bring in more tax revenue. Proposition 2½ limits the amount of property tax revenue a community can raise through real and personal property taxes.

“We know teachers and staff want to be back in the classroom, and we want them back in the classroom with students. But we cannot responsibly approve a contract that ties the hands of the district and the town for years to come,” the school committee said Monday.

The union said in a statement late Sunday that the school committee “made no effort to reopen schools as the contract proposal offered to the striking Andover Education Association failed to achieve our goals of raising instructional assistants above poverty wages or address fair raises for teachers.”