It was a moment for the charter school movement to show its muscle. Wearing red shirts that said “Don’t Steal Possible” and “I’m a teacher who believes,” ten thousand or more students, parents, and teachers converged on Foley Square this morning for a rally in support of Charter Schools.

Their aim was a show of strength in the test of wills between a charter school movement energized by Eva Moskowitz, a possible future contender for mayor, and Mayor de Blasio. The mayor is an opponent of charters and issued a broadside against the movement even while the rally was being held.

Early in Mr. de Blasio’s term, Ms. Moskowitz mounted a major rally in Albany, helping to bring Governor Cuomo to the rescue in the battle over the allocation of space for charter schools in the city and elsewhere. The rally today in Foley Square was a show of strength of the movement in the city.

While parents and children waved signs that said “Kids can’t wait” and “Great schools now,” Assemblyman Robert Rodrigues told the crowd that he was “to say that more than 143,000 students citywide are stuck in failing schools.” Declared Mr. Rodrigues: “That’s not a statistic, that’s a crisis.”

The statistic comes from Families for Excellent Schools, a pro-charter organization whose Web site uses 143,000 for the number of students trapped in what it calls “persistently failing schools.” It says that one in four city schools are “failing 90% of their students.” It says that “out of a class of 30 minority kindergarteners, only 2 will graduate ready for college.”

Mr. de Blasio, clearly irked by the rally, releasing today a slickly produced video declaring that the answer to the crisis in education was not to find an “escape route that some can follow and others can’t” but to “fix the entire system.” The video boasted that every child in the city would have to chance to go to a pre-kindergarten “for free.”