The Chicago Teachers Union said districts across the state will face severe budget shortfalls if officials don't act fast.
The group spoke outside Mollison Elementary School in Bronzeville on Monday morning. Organizers said the school has the highest vacancy rate in the city, and has been on the "closure list" twice.
Schools across the country are set to lose $200 billion in federal pandemic funding.
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"We just need the support; we need the funding. We got an email last week, saying we're going to have to start buying our own copy paper," Mollison Elementary teacher Alayne Pierce-Collins said.
Teachers at Benito Juarez High School in Pilsen are also worried about the lack of bilingual support staff, inadequate facilities and cuts to extracurriculars, like arts education, will harm students.
CPS serves 20,000 new English Language Learners, a growing number of homeless students and over 76% of students from low-income families.
They are the ones, organizers say, who stand to lose critical services, like social workers, librarians, arts and after-school activities, as federal support disappears.
The final $122 billion phase of the Elementary and Secondary School Emergency Relief fund, or ESSER, a part of the American Rescue Plan law signed by President Joe Biden in March 2021, was distributed to state and local education agencies to reopen schools and promote physical health, safety and mental health and well-being.
In total, that funding and two prior installments of ESSER during the 2020 pandemic is roughly $190 billion.
Chicago Public Schools CEO Pedro Martinez responded to teachers' demands at an event Monday morning.
"Our plan is going to be to ensure our elected officials how we're using the resources, the gains we continue to make and really showing them the investment in CPS is working," he said.
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Teachers called on Gov. JB Pritzker and other elected officials to fund Illinois public schools.
CPS is facing a $500 million shortfall.
CTU holds 'walk-in' as district faces $500M shortfall
The walk-in, which included CTU President Stacy Davis Gates, came as a fight continues to grow over leadership within Chicago Public Schools.
A book donation event brought Martinez to a school on the North Side. While, at the same time, Davis Gates was on the South Side.
"We are about winning more funding for our school system, and he is not," Davis Gates said. "He said he would give them 5% raise, but what he didn't say out loud is you have to take furlough day."
Davis Gates continues to publicly turn up the heat on Martinez, after the Chicago School Board took no action last week at its monthly meeting on the CEO's contract. Martinez refused to step down, after he said Mayor Brandon Johnson asked him to resign.
"I would say this is much bigger than me. This is about ensuring that our district has stability," Martinez said.
Martinez received a letter of support from several lawmakers and two former CPS CEOs. All had concerns about removing Martinez, as students are making academic gains, and during CTU/CPS contract negotiations.
While Davis Gates has made it clear Martinez must go, the mayor denies putting pressure on school board members to fire him. Johnson is also now denying asking Martinez to resign.
"I didn't ask anybody to do anything, didn't ask anybody to do anything. The only thing I'm requiring in this moment is leadership prepared to invest in our children," Johnson said.
Johnson and Davis Gates turned on Martinez after the CEO refused to secure a short-term high-interest loan to pay for a new teachers contract and pension payments.
Martinez has yet to come up with revenue ideas to shore up the projected budget gap.
The union said furloughs and layoffs are on the table. Martinez said it is only a last resort if CPS meets all of CTU's contract demands.
"We are getting a lot of pressure to spend more resources, and, I want people to know: We need to secure the revenues, and I'm more than happy to invest," Martinez said.
Martinez plans to discuss more about revenue options when he will appear before City Council's Budget Committee on Thursday. Its chairman, Alderman Jason Ervin, supports the ouster of Martinez.
Martinez will be asked about revenue options, pension payments and teacher contract negotiations Thursday.
ABC News contributed to this report.