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."

And his favourite is one of the scariest and most well known, the Tyrannosaurus Rex!
Prince George's Mum, Kate Middleton, revealed to children which dinosaur was his favourite during a visit to the Natural History Museum.
She said "George loves the T Rex because it's the noisiest and the scariest."
Kate was visiting the museum for a special children's tea party being held to say goodbye to Dippy the Dinosaur.
Dippy is the museum's most easily recognised exhibit, a massive 21.3m model of a Diplodocus skeleton and was presented to the museum more than 115 years ago!
It is being packed up and sent on a tour of the UK, so every piece must be labelled and packed away. A job that's about as big as dippy is!

Cyril Banks, 91, had £9,000 stolen from him by fraudsters who pretended to be from the Met Police, officers said.
The Herts and Essex Observer set up a fundraising page after Mr Banks, from Bishop's Stortford, was interviewed on BBC Three Counties Radio.
Mr Banks said he had been "overwhelmed" by the generosity.
"It's unbelievable. I didn't realise people would offer so much," he said.
Read more on this story and other Hertfordshire news
So far, £12,034 has been raised by 455 people since the page was created on Thursday afternoon.
Hertfordshire Police said an investigation into Mr Banks' case was ongoing.
Mr Banks' friend Annie Riley said she had been "appalled" by the people who had persuaded him to withdraw £9,000 from his bank account.
"I don't know how they sleep at night," she said. "Cyril's such an amazing and giving man, he's always collecting for charity.
"At least by talking about what happened to him, we might have stopped someone else from falling victim to the scammers."
Paul Winspear, editor of the Herts and Essex Observer, said the response to the fundraising page had been "amazing".
He said: "We had a lot of comments on our Facebook page about what happened to Cyril and people were asking how they could help him, so we set a page up.
"We hit the £9,000 target within about six hours."
Mr Banks said he had even been offered £40 by a young man who overheard him telling a friend what had happened.
"It's wonderful to see such kindness and generosity," he said.
Mr Banks said he would give any money over the £9,000 he had lost to charities he supported.
"If I can help other people out of this and give back what they've given to me, I would feel I am repaying their generosity".
A march has taken place backing three striking cleaners who say their wages and employment benefits have been cut.
[NEXT_CONCEPT]
We all love dinosaurs and Prince George is no exception.
[NEXT_CONCEPT]
An online fundraising campaign to help a World War Two veteran, who was defrauded out of his life savings, has raised £12,000 in less than 24 hours.