Following up, the ProJo has their report on the situation today:

School officials said that few members of the union that represents custodial, maintenance and secretarial employees — the Warwick Independent School Employees (WISE) –– responded to calls to come to work late Sunday afternoon even though union workers had showed up for snow duty on Friday and Saturday.
The School Department and the WISE union have been stalemated over a contract for more than two years, but union leaders last night said that there was no concerted attempt to avoid working on Sunday.
Mayor Scott Avedisian, who was in contact with both sides yesterday morning, said he did not care which was in the wrong and that it is “absolutely unacceptable” that Warwick schools were not ready to open along with almost all other public school districts yesterday.
To prevent a repeat occurrence, Avedisian said that after talking to School Committee Chairman Christopher Friel in the morning, he issued an executive order forming a special committee to deal with efficient snow removal at the schools. He said that he and Friel agreed that if school employees are not available to clear the drives, parking lots and walkways, the city will do the work and bill the School Department.