Organizers have rescheduled the charter-school parent rally planned for Wednesday because of inclement weather, according to a spokesman for the advocacy group Families for Excellent Schools.

The event was expected to draw more than 10,000 parents, students, and teachers from prominent charter school networks, but was called off after forecasts showed that thunderstorms were likely to hit New York City in the morning. It will instead take place Oct. 7, a delay that could extend a recent spate of advocacy efforts from the city’s teachers union and other opponents.

The event had promised to reawaken a long-running campaign to undermine de Blasio’s vision for public education. Like those held in past years, it was expected to draw a long procession of families, most of whom are black and Hispanic, and attract a great deal of media attention. The singer Jennifer Hudson and DJ Jazzy Jeff were both scheduled to perform, and Bronx Borough President Ruben Diaz, Jr. was supposed to speak, according to organizers.

The rallies, which Families for Excellent Schools has staged since 2013, have become a potent weapon in the larger political battle the group is waging with the teachers union to influence education policy in the city and state. That battle has intensified as charter-school enrollment has grown to nearly 100,000 students and the city government under Mayor Bill de Blasio has cooled to the charter movement, which grew rapidly under former Mayor Michael Bloomberg.

The rescheduled event will come soon after de Blasio unveiled a new array of his own education initiatives, including an expansion of computer science education and the addition of literacy coaches to help struggling second graders. This month, a number of other significant city education initiatives have begun in earnest, including the extra support services being installed at the city’s struggling “Renewal” schools and another set of schools set to become “community schools.”

Opponents say the city’s plans don’t do enough. The sustained attention on that opposition could pose problems for de Blasio as he begins to make his case to lawmakers that they should give him control of the city’s schools for longer than one year.

Leading up to the event, Families for Excellent Schools had stirred up controversy with a provocative ad attacking inequity in New York City schools. The ad, titled “A Tale of Two Boys” in a play on de Blasio’s own campaign slogan, depicts a black boy whose life trajectory is stunted because of his education next to a white counterpart headed for success.

Allies of the mayor called the ad “race-baiting” this week, and asked Families for Excellent Schools to pull the ad, which a spokesman said the group would not do.

De Blasio himself has tried to keep attention on his own initiatives, discussing his $81 million plan to train teachers to teach computer science over the next decade in an interview on CNBC’s Squawk Box on Tuesday morning.

“It will obviously be the largest school system in America devoted to ensuring that every kid has this opportunity,” he said.

Meanwhile, City Council members, teachers union President Michael Mulgrew, and civil rights groups have raised old and new critiques of the charter school sector. At an event Monday, many condemned the ad, and others said they were uncomfortable that parents and children from Success Academy charter schools and other networks planned to participate in the rally at a time when students would ordinarily be in school.

City Councilman Daniel Dromm, who chairs the council’s education committee, alluded to Eva Moskowitz — a former city councilwoman who runs the Success Academy schools and has been open about her interest in running for mayor — in his critical remarks.

“If she’s not running for mayor she should say she’s not running for mayor, or she should step down from her position as the leader of that charter school because we should not be using our children as political pawns in the fight over the charter schools versus our district schools,” Dromm said.

UFT President Mulgrew reserved his criticism for a new law that allows charter schools to give preference to children of their employees in their admissions lotteries. He also rejected Moskowitz’s claims that the city’s school system is failing the most disadvantaged children. Under de Blasio, there were already signs of improvement, Mulgrew said.

“In New York City, this is the beauty of it, you see that our school system is moving forward,” Mulgrew said.

De Blasio has been a target of the rallies since he emerged as the frontrunner to replace Bloomberg in 2013. He attracted the ire of charter advocates then for promising to charge rent to charter schools operating in city-owned buildings and for specifically calling out Moskowitz’s schools.

The next year, organizers rallied parents around what they called a “failing schools crisis.” That event was meant to put pressure on de Blasio to come up with a plan to improve the city’s worst-performing schools.

In the two legislative sessions that followed, charter school advocates scored major victories, including a law that guaranteed that most new and expanding New York City charter schools would have access to free space or get city funding to pay rent.

Charter school consultant Dirk Tillotson said he questioned whether the rallies are productive. But in terms of changing the nature of the charter sector’s relationship with de Blasio, “It’s gotten his attention and it’s put him on his heels,” he said. “So I think they’ve gotten the effect they’ve wanted to some degree.”