For the families of Los Angeles Unified School District students, Monday unfolded with mounting uncertainty — and, for many, deep anxiety — as it remained unclear by the close of the school day whether campuses would shut down amid a potential strike by three unions.

Two of the unions, representing teachers and administrators, reached tentative agreements over the weekend. As of Monday afternoon, Local 99 of Service Employees International Union, which represents some of the district’s lowest-paid employees had not settled. In solidarity, all three unions have pledged to walk out together if any one of them did not make a deal.