Cleaners at Sheffield’s Park Academy struck last Wednesday for £7.45 per hour living wage.
The current hourly rate is £6.32—just 1p an hour above the national minimum wage.
The GMB members are employed by contractor Ocean. Their jobs were out-sourced by United Learning Trust to Ocean earlier in the year as a way of avoiding paying the living wage.
After walking out strikers later put questions to a meeting of Sheffield City Council. They want councillors to force firms to pay up.
Despite successes at Veolia, Amey, Norse, Enterprise and Green Co most council officers and partners find ways around it.
A union spokesperson said it was time to demand a living wage for the lowest paid workers in all schools and the public sector.