The state government in 2018 awarded facility management company ISS the cleaning services contract for more than 200 public schools in Melbourne's west and northeast.
The contract was up for renewal this year but after a to-and-fro about the length of an extension amid a review, a deal couldn't be struck and the government opted to go with different contractors, the United Workers Union said.
The decision has impacted hundreds of school cleaners who fear they will have their hours reduced, probation periods renewed and lose banked sick leave and years of service, slashing their redundancy entitlements.
ISS has committed to working with the incoming contractors to try to keep cleaners at their usual schools.
ISS, which confirmed it did seek an extension to the contract, has also offered jobs to anyone who doesn't stay on with the new contractors, a company spokesman said.
"ISS has engaged with United Workers Union to support employees' transition to the new service providers and ISS will have opportunities for redeployment for employees who do not accept employment with the new providers," a company spokesman said.
But the offer wasn't enough to quell the concerns of cleaners who face significant disruption and a potential pay cut when the contract runs out in December this year, the union said.
Among the concerned workers is 50-year-old Ines Lizama who was shocked when, after five years of working for ISS, the company last month announced the contract was ending.
"The anxiety and frustration that people are suffering right now (is because they worry) will they be secure with the next company that's coming on board," she told AAP.
"If we haven't got it in writing, we're not secure at all.
"We're always the last ones to know about everything that's going on."
School cleaners wanted clarity about whether they would maintain their hours and shifts under the incoming contractors before the ISS agreement ran out, Ms Lizama said.
The government is yet to announce the incoming contractors.
The United Workers Union has lobbied the Department of Education to scrap the contracting arrangement for school cleaners and instead hire them directly.
Ms Lizama said this would ensure school cleaners had better conditions and were treated with more respect.
The union has worked with the government as it reviews how it delivers cleaning services in public schools.
"More often than not, (school cleaners are already) working two jobs and are struggling to make ends meet on very low wages," union co-ordinator Linda Revill said.
"ISS pulling out and a new contractor coming in provides a clear illustration of everything wrong with this contract service delivery model."
The union wants the state government to guarantee jobs for affected ISS cleaners, secure them the same pay and hours, scrap any probationary period and approve any unpaid leave for 2024.
A Department of Education spokesman said it was overseeing the ISS transition and working with service providers to ensure a smooth process for schools and cleaners.
"The Victorian government is currently exploring opportunities to strengthen the delivery of cleaning services in government schools," the spokesman said.
The department in 2018 rolled out an area-based cleaning model for more than 600 metropolitan public school campuses.
The number of school campuses has since grown to more than 900.
