Marice Hall, Karen McGee and Lesley Leake work at a Kinsley primary school near Wakefield. They said pay had been cut since it became an academy.
After the contract moved from Wakefield Council to private company C&D Cleaning pensions, holiday and sick pay had also been cut, they said.
C&D said it was seeking to resolve the matter as quickly as possible.
About 100 people marched in Barnsley, where C&D is based, from the Town Hall to the town centre.
The three women have been on strike since the beginning of September, with the union Unison taking the employer to an employment tribunal.
Lesley Leake said: "We had just had enough, we were sick of going home and crying to our partners.
"It has been scary, but we have just got to go to the end and see how it turns out."
Marice Hall said: "We love our little job and we just want to carry on with our normal lives and go back to work."
Robin Symonds, regional organiser for Unison, said: "It's probably the worst example that I've ever seen, and I've seen some pretty bad examples of low-paid workers who have had their jobs outsourced being thrown to the wolves by greedy employers".
In a statement, a spokesperson for C&D said: "C&D were not provided with crucial information at the point of transfer of the three employees.
"We will not conduct a public discussion over the issues, as they are and will be dealt with in an appropriate manner.
"C&D is actively seeking, as it has all along, to resolve this matter as quickly as possible."
A march has taken place backing three striking cleaners who say their wages and employment benefits have been cut.