The workers - including teaching assistants, caretakers, caterers and admin staff - could have their pay slashed by up to 25 per cent if they sign new contracts which mean they will only be paid for term time, rather than all year round, according to the GMB union.
The changes have sparked fury among support staff and other school workers in the county, who fear they could lose their jobs in they don't agree to the terms.
The schools involved have not been named but it's understood they are academies rather than council-run schools.
Some schools are also said to have upped the full-time equivalent requirements for support staff from 32.5 hours to 37, without allowing them to work longer, meaning they get a wage cut.
One teaching assistant, who asked to remain anonymous, said: “I’m being forced to do the same job for almost a quarter less pay. Me, my family and pupils are all suffering.
“I’ve dedicated my life to the job I love but I don’t know how long I can keep going. They wouldn’t do this to teachers.”
Kirsty Hackney, GMB organiser, said: “Support staff are the loyal, hard-working foundation of schools; they're helping to raise the children of our communities.
“During the past year, many schools allowed teachers to work from home while teaching assistants and support staff were on site with key workers’ children putting themselves at risk for the benefit of the children.
“They come in early and go home late - staff stay for after school clubs and meetings - and they do it all for our children."