MANASSAS, Va. (AP) — A northern Virginia teachers’ union is apologizing after some of its members used child-size coffins as props at a protest seeking to delay in-person education.

The Prince William Education Association posted the apology on its Facebook page early Thursday. The union said that 100 cars participated in the protest caravan Wednesday, and that two of the cars were decorated in a way that some found offensive.

School boards across Virginia and the U.S. are weighing plans to transition students forced into virtual learning because of the coronavirus pandemic back into the classroom. Many teachers’ unions have voiced opposition, citing concern for staff and students’ safety.