Battlelines have been drawn weeks after councillors in South Ayrshire announced a multi-million pound package of new schools and upgrades.
Paul Arkison, a union regional officer with GMB Scotland, spoke out at a time when local politicians grapple with cost cuts of £4.6m for the coming year.
Education bosses operate kitchens at 36 of their 51 schools. The GMB claim half the kitchens could be axed with jobs under threat among 60 school crossing patrollers and 290 school assistants.
Mr Arkison claimed the jobs of janitors and caretakers are under threat along with the number of hours spent cleaning schools.
But he warned: "However, there is only so much you can mitigate against and with these devastating proposed cuts there will undoubtedly be job losses and this will increase the risk of pupils' safety and well-being in and around the schools which they attend.
"Members are stunned that elected councillors could vote through such proposals. Some of the options beggar belief. For example, closing school kitchens while the Scottish Government has made a commitment to give Primary 1, 2 and 3 pupils free school meals from January, 2015."
Council leader Bill McIntosh, denied the "safety and wellbeing of our pupils" would be put at risk when he and other colleagues agreed "efficiency savings."
He said: "Our priority is to agree suitable service standards within our schools and ensure staffing levels are fit for purpose"
He said £55m was being invested in schools.