(CNN) Striking Los Angeles teachers rallied in front of City Hall on Friday, one day after the teachers union and the school district went back to the negotiating table.

More than 30,000 educators walked off the job Monday to demand smaller class sizes, more school staffing and higher teacher salaries.

"We are having an impact," said Alex Caputo-Pearl, president of the United Teachers Los Angeles union. "That impact is being felt across the city. And we've just got to keep it up."

Tyler Okeke, the student member of the LA School Board, issued a statement on Twitter urging compromise: "If the Los Angeles Unified and UTLA are to come to a peaceable contract agreement, concessions on both sides will have to be made," he tweeted.

But while teachers demand millions more dollars in school funding, the Los Angeles Unified School District said it has already lost $125.1 million during the strike through Friday

That's because the state of California funds schools based on daily attendance, and the number of students going to school has plunged during the strike.

Friday, for example, 85,274 of the district's 600,000 students went to school, the district said, noting that number is incomplete because 18 schools had yet to submit reports through the system's internal attendance system.

Thursday, about 84,000 students went to school, the district said, noting that number may still be adjusted. That's a 37% drop in attendance from Wednesday.

Parent Karen Goldman said she is well aware of the money lost by lower attendance. That's one reason she's keeping her fifth-grade son out of school.

"I feel like the message I am sending by not sending him and creating a budget loss is better than if I send him, because that will hopefully bring the strike to a conclusion faster," she said.

But don't expect teachers to end their strike anytime soon, the union president said Thursday.

"After 21 months of negotiations, I think it's an unrealistic expectation to say that this is going to be over after today," Caputo-Pearl said.

The teachers on strike are not getting paid. But the union leader said it's critical for them to outlast district Superintendent Austin Beutner, a former investment banker who doesn't have a background in teaching.

"If it goes into next week ... we have to last one day longer than Austin Beutner," Caputo-Pearl said. "We have to last one day longer than somebody who's never taught in a classroom."

"Negotiations continued today," the school district said on its website . "Los Angeles Unified remains committed to working around the clock to find a solution that ends the strike."

The school district says kids are still learning

Even though students are supposed to go to school during the strike, many parents have pulled their kids out because of the shortage of teachers.

Some students who did go to school reported playing board games or watching movies all day

But the school district said students are learning -- though sometimes in auditoriums rather than classrooms. At Adams Middle School, an assistant principal filled in and gave a history lecture Thursday.

Outside Los Angeles City Hall families and educators make the stand for public education.#WeAreLA #UTLAStrong #Red4Ed #WeArePublicSchools pic.twitter.com/b6RKHvToHj — United Teachers Los Angeles (@UTLAnow) January 18, 2019

Last week, the district said 2,000 reassigned administrators and about 400 substitute teachers would help fill in for the more than 30,000 educators on strike. Wednesday, the school district updated the number of substitutes to 1,400.

The district has not responded to CNN's questions about how many teachers are not on strike and are still in classrooms.

Schools continue to do their best feeding our students. In celebrating Dr. King's birthday, we have a dream that soon our teachers will be back to continue nourishing our students hearts and minds. @lausd_ldc @LASchools @SomosLAUSD pic.twitter.com/UelRlO6bWS — LD Central (@lausd_ldc) January 18, 2019

Beutner has defended the decision to keep schools running -- especially for lower-income families, who can't afford child care and don't have a safe place for their children to go.

"While education in classrooms is not the same without teachers, we have a responsibility to keep schools open and provide students with a safe space, shelter from the rain, meals and modified instruction," he said.

The big fight over money -- and one big agreement

This standoff comes down to two issues: how much money to spend on more school staffing and teachers' raises, and whether the school district has that kind of money.

Beutner said there's no way the district can afford right now to give the union everything it wants. He noted an independent fact-finder agreed that it doesn't have the money to cover the union's demands.

The district did offer $130 million toward what the union wants, but it rejected that proposal.

Today @LASchools presented UTLA with a new offer to significantly reduce class size and ensure no increase in any class size, increase nurses, counselors and librarians at all schools, along with a 6% salary increase and back pay for the 2017-2018 school year. pic.twitter.com/jchW2fCHsm — L.A. Unified (@LASchools) January 12, 2019

The teachers union said the school district should tap into $1.8 billion in reserves to fund more staff members and increase teachers' pay.

But the union president said the school district has "always been wrong in their projections, so we just don't believe those numbers."

"Three years ago, they predicted a $105 million reserve; they ended with a $1.86 billion reserve. They were off by $1.7 billion, Caputo-Pearl said.

If there's one financial matter both sides agree on, it's that they need more help from the state. About 90% of the district's funding comes from Sacramento, Beutner said.

Newly elected California Gov. Gavin Newsom has proposed an increase in public school funding and wants the stalemate in Los Angeles to end soon.

"This impasse is disrupting the lives of too many kids and their families," Newsom said in a statement Monday.

"Last week, I submitted a budget to the Legislature that would make the largest ever investment in K through 12 education , help pay down billions in school district pension debt and provide substantial new funding for special education and early education."

But it's not clear exactly how much additional money Los Angeles schools might get, or when.