CHICAGO – Elfega Cazares isn’t taking sides in the standoff between the Chicago Teachers Union and Chicago Public Schools over contract talks.

Like many of the immigrant parents in the city’s Pilsen neighborhood, she knows her children stand to lose the most if teachers walk off the job next Monday.

“It is very important that we stay in school so we can be prepared to be someone in life,” Cazares said, her 10-year-old son Francisco Vasquez translating for her from Spanish.

But students across the city, most of whom return to school Tuesday, could find themselves out of the classroom again Sept. 10.

At a time when teachers’ unions are under pressure nationwide, union President Karen Lewis said more than 26,000 teachers and support staff in the nation’s third-largest school district are prepared to strike for the first time in 25 years.

It would be the first big-city strike in the United States since Detroit teachers walked off the job for 16 days in 2006. The last Chicago teachers strike was in 1987 and lasted 19 days.

School officials and parents shifted into high gear after the union issued a 10-day strike notice last week, trying to decide what to do with 400,000 students, including those in neighborhoods beset by gangs and struggling with a spike in shootings and homicides.

District officials said they would chaperone students during the morning in 145 schools, and invited bids from community organizations to provide “positive activities” the rest of the day.

The pending walkout presents other problems, too. College applications would be delayed. Varsity sports, from football to diving, would be suspended for 11,000 athletes. More than 20,000 juniors could miss practice tests for ACT exams.

Near Manuel Perez Jr. Elementary School in Pilsen, an enclave of Mexican immigrants where the public school plays a central role for almost everyone, the concerns were of a long-term nature.

Working-class parents like Cazares say they would have to find a family member or someone to watch their children while they work, but their bigger fear is children will lose ground on attaining the better life the parents uprooted and crossed borders to pursue. In Pilsen, a good education means children won’t have to follow their parents into low-paying jobs.

“They tell us how they didn’t get an education, that we must get one for our future,” said 19-year-old Connie Diego, whose younger brother is in fifth grade. “We couldn’t ever miss even a day because our parents tell us about all the benefits we have there and how where they came from they didn’t have anything.”

Local activist Fernando Rayas points to children like Vasquez, who must help their immigrant parents communicate. Students learn English at school, he said, not at home. Depriving them of the opportunity, he said, means “they will fall behind.”

Mayor Rahm Emanuel, who lengthened the school day this year and says he wants to better hold teachers accountable for student performance, has a lot riding on the negotiations. So do teachers, who are upset Emanuel canceled a previously negotiated 4 percent raise and fear the district wants merit-only raises tied solely to student achievement.

The two sides appeared to have settled a primary issue when they agreed laid-off teachers would be rehired to cover the longer school day instead of paying existing teachers more, but bargaining and posturing over several remaining issues has continued.

The union put on a show of strength on Labor Day, packing a downtown plaza beside City Hall with thousands of supporters. Addressing the crowd, Lewis called Emanuel a “liar and a bully,” the Chicago Sun-Times reported.

Emanuel — and the contract negotiations — will be in the national spotlight this week, just days before the strike date: He’s scheduled to address the Democratic National Convention.

In Pilsen, people are quick to point out how important the school is to the entire community, located southwest of downtown.

Ninety-five percent of the 430 preschool-through-eighth-grade students at Perez elementary qualify for free or reduced-price lunches, Principal Vicky Kleros said.

Even so, it’s been designated as a fine- and performing-arts magnet cluster school, and earned a Level 1 ranking for academic performance. It also was one of the first CPS schools to implement the rigorous new national Common Core curriculum, meant to improve performance in subjects such as math and reading.

Perez is also an important neighborhood resource, a place where parents can take courses in technology, learn to read and write English and work toward a general equivalency diploma, Kleros said.