Teachers in the nation’s third-largest school system took to the picket line for a second day Friday, continuing a strike that centers on working conditions inside Chicago public schools.

The labor strike by the 30,000-member Chicago Teachers’ Union affects 300,000 students.

Salary and benefits are at issue, but the teachers’ union has put more emphasis on other issues.

Art teacher John Houlihan said he was walking the picket line outside Smyth Elementary on Chicago’s south side because he wanted better conditions for the students he teaches.

“It’s ridiculous to say that you can put these kids who are dealing with profound poverty and profound homelessness in classes of 30-40 kids,” said Houlihan, who picketed with about 20 other teachers and staff as drivers passed by, honking their horns. “That’s not manageable and it is not an environment for learning.”

At one Chicago school, Edwards Elementary, just one counselor is available to 1,400 children, the union said.

The issues should sound familiar to Philadelphians, since the Philadelphia Federation of Teachers has long said classes are too large inside many of its city’s schools. The union also has called for more counselors, nurses, and support staff, another theme of the Chicago walkout.

Chicago teachers last walked the picket line in 2012, when the district’s finances were tighter. Now, they say, school district leaders must cooperate on issues that would improve the lives of district children, who, like Philadelphia public school students, are mostly poor kids of color.

The CTU’s focus has shifted in the last 10 years since a social-justice leadership team took over. In Philadelphia, a similar group, the Caucus of Working Educators, challenged current PFT president Jerry Jordan’s team during the union’s last election, and has vowed to do so again, when PFT members elect officers early next year. Jordan won by a resounding margin nearly four years ago.

Lori Lightfoot, Chicago’s mayor, said she wanted to add 250 new nurses, 200 social workers, and more staff to help manage special education children’s cases, but she initially balked at enshrining her commitment in the teachers’ contract.

A wave of teacher strikes in the recent past has given labor leaders a road map. Los Angeles, the nation’s second-largest school system, went on strike this year over similar issues. That strike lasted seven days.

PFT president Jordan said at the time that he saw parallels between the L.A. strike and Philadelphia’s looming contract situation.

The PFT’s contract expires in August. Negotiations for the next pact are expected to begin soon.

Jordan has said he is optimistic an agreement will be reached and that a strike will not be necessary, but the PFT has the power to strike next year, unlike in the past, when the state takeover law prevented Philadelphia teachers from walking off the job.

In Chicago, Lightfoot said this week that she could add some of her promises regarding class sizes and new staff to the contract.

Most recently, city negotiators suggested the CTU lacked urgency in negotiations and requested that both sides spend 10 hours every day at the bargaining table. Union officials scoffed at the idea that they were not serious about bargaining.

Some parents and even children walked picket lines with teachers, but others were grappling with child-care issues.

Chicago school buildings were open for children who need a safe place to stay, district CEO Janice Jackson said. Officials also suggested parents send children to public libraries and certain community organizations.

This article contains information from the Associated Press.