Charter school teachers hit the picket lines for the second day in a row as union and charter supporters traded verbal jabs at a meeting of the Chicago Board of Education Wednesday.

Rank-and-file members of the Chicago Teacher Union continued their fight for an increase in pay for teachers and paraprofessionals, a reduction in class size and enhanced special-education resources at Acero Charter Schools — one of the city’s largest charter school networks.

While meetings between officials with Acero and union negotiators have not led to a solution, pressure is building to settle the nation’s first-ever charter school strike, union members said.

“It is very apparent to us that Acero is feeling the pressure,” teacher Martha Baumgarten said. “We can sense at the table that there is a bit of urgency and that all comes back to our members standing strong by holding picket lines at their schools.”

Baumgarten, a fifth-grade teacher at Acero’s Carlos Fuentes Elementary School, has been sitting at the bargaining table for seven months. She hopes an agreement can be reached but said CTU members were gearing up for another day of picketing — a move that will force 7,500 students out of school for a third day.

As of Wednesday evening, some of the key issues like increased wages for paraprofessionals and creating sanctuary schools — teachers want the schools to provide resources to undocumented students and ban the sharing of information with immigration officials — had not yet been resolved. Bargaining was expected to continue through the night.

Acero officials, though, said things were moving forward.

“There continues to be productive movement on both sides,” a spokeswoman said in a statement. “We look forward to getting our teachers and students back into classrooms as quickly as possible.”

The statement said Acero was proposing average raises of 6 percent for each year of a 4-year contract. It said the charter network had agreed to a step schedule for non-instructional staff.

Meanwhile, Jesse Sharkey, CTU’s president, appeared in front of the Chicago Board of Education, to express his dissatisfaction with how Acero has managed its money and why it forced the strike of 550 workers.

“The latest audit of Acero shows that they have $10 million of additional revenue year over year, yet classroom spending in that network has decreased by nearly $1 million, or 6 percent of their budget,” Sharkey said. “In other words, [CPS] is handing over piles of cash and less of it is going into the classroom.”

Sharkey said a recent audit showed Richard Rodriguez, Acero’s CEO, made more than $260,000, a slightly higher salary than CPS CEO Janice Jackson. Rodriguez watches over 15 schools whereas Jackson oversees more than 500.

Rodriguez has not attended any of the 30 bargaining sessions that have been held in the past seven months, according to Baumgarten.

Acero chief external affairs officer said Rodriguez’s compensation is “competitive with other like-sized charter school networks and non-profit organizations and, historically, that of CTU’s leadership.”

“We know that [Acero] is stockpiling cash, there’s over $24 million in cash reserves in that network at the same time that we’ve seen a reduction to the resources that are going to the classrooms, and that’s provoked the first strike,” Sharkey said.

But Andrew Broy, president of the Illinois Network of Charter Schools, said the high reserves are required.

“The fact of the matter is CPS’ own internal policy requires all charter public schools to have a reserve fund,” Broy said. “And good nonprofit governance suggests 90 days of reserve funds, so it’s not a problem of the system, it’s a feature of the system.”

The ultimate goal for the CTU is to standardize union contracts for all charter school teachers, Broy said. He argued charter schools approach to education has been innovative — pointing to longer school days and improved student learning — without the use of union teachers. This innovative practice would be stifled with continued unionization, he said.

“Such a one-size-fits-all policy is not only bad for students, it’s terrible for Acero and it’s the exact opposite of innovation that’s the hallmark of the charter-school community,” Broy said.

Manny Ramos is a corps member in Report for America, a not-for-profit journalism program that aims to bolster Sun-Times coverage of issues affecting Chicago’s South Side and West Side.