It came as no surprise to Sol Stern of the Manhattan Institute that a class of New York City public high school pupils took a spring break jaunt to communist Cuba. “Sure, they do it every year,” Mr. Stern told me. He sees this as part of something much larger, a cadre of leftists and others caught in a time warp, promoting a 1960s type of radicalism. The problem is, according to Mr. Stern, that they are doing it in the public schools.

Although the city’s education department has rules about nearly everything that goes on in our schools, when it comes to the manipulation of young minds for political ends, not only does there appear to be no effort to stop such practices, but the mayor and chancellor have become unwitting co-conspirators in promoting them.

The New York Post reported Monday that perhaps a dozen students from the selective Beacon School, a public high school on Manhattan’s West Side, made the trip to the imprisoned island accompanied by their history teacher, Nathan Turner. Such a trip violates American law, and the participants face warnings or fines that could be as much as $65,000 each.

Mr. Turner is reported to have decorated his classroom with posters of such Cuban luminaries as the island’s ailing dictator, Fidel Castro, and the Marxist Che Guevara.

Although Beacon’s principal, Ruth Lacey, maintained that this year’s trip was not school-sanctioned, it was promoted, according to the Post, on the school’s Web site. And Ms. Lacey acknowledged that previous trips to Cuba in 2004 and 2005 had been approved. Travel restrictions have been in place since 1962 and were tightened in 2003, before the school’s first trip there. Therefore, it is clear that the administration of the school cooperated in breaking the law in previous years even if the 2007 trip lacked official school approval.

Last year, the school trip was to Venezuela, presumably a show of solidarity with its anti-American president, Hugo Chavez.

It isn’t just on the foreign policy front that radical activists have gained a foothold. Mr. Stern notes that the leadership of the Department of Education has accelerated the creation of schools with so-called social justice themes. Many of these schools were created using funds provided by Microsoft’s founder, William Gates, the world’s richest man. Mr. Stern believes there are at least 15 such new schools, almost all created during the current administration. Some of these are affiliated with left-wing groups such as Acorn and the Northwest Bronx Community and Clergy Coalition.

Even after the New York City Police Department charged that the latter group “coached” students to falsely accuse police, at a City Council hearing, of maintaining order at Walton High School in the Bronx by setting off stink bombs, the education department approved the linkage between the Northwest Bronx Community and Clergy Coalition and the newly created Leadership Institute high school. Solicitations for new teachers in that school have been routinely filtered through the Northwest Bronx group, presumably for political appropriateness.

Beginning April 27, a national conference centered on the New York City public schools, titled “Math Education and Social Justice,” will take place. The conference will be held at El Puente Academy for Peace and Justice in Brooklyn, the first of Gotham’s “social justice” public schools, described by Heather MacDonald in her article “An F for Hip-Hop 101,” which appeared in the summer 1998 issue of City Journal.

How is math education radicalized? A typical “formula” might “prove” that the devastation to New Orleans resulted not from the natural disaster of Hurricane Katrina but came as result of racism is America.

Among the “expert” speakers at this event will be Cathy Wilkerson, an adjunct professor at the Bank Street College of Education. If the name sounds familiar to those of us of a certain age, it is because Ms. Wilkerson was a member of the Weather Underground who gained national prominence in 1970 after she escaped from a Greenwich Village townhouse that was destroyed when a terrorist bomb that was being manufactured there prematurely detonated. After resurfacing and serving a prison term, she became a high school math teacher.

The New York Collective on Radical Education is listed as a co-sponsor of the math conference. No fewer than eight hands-on demonstrations are planned as part of the three-day event at New York City public schools, using teachers paid by the Department of Education and New York City public school children as props. The conference has been brought to the attention of top officials of the Department of Education, who have refused to address the appropriateness of such a conference or the use of city personnel, facilities, and students.

The intersection of radical politics and education is not limited to simply the traditional political left and right. The Department of Education recently announced that it was permitting the creation of the Khalil Gibran International Academy for the study of Arab language and culture. This school will occupy the upper floors of P.S. 252 in Park Slope, much to the chagrin of parents there.

The public schools should not be used to advance the politics of any individual or group, whether it is the pro-Castro teacher at the Beacon School who is still fighting the Cold War, the math teachers looking to change societal priorities to something more to their liking, or Islamists who see the potential of a mini-madrassa in Park Slope.

My guess is that Mr. Klein understands that the Cuba trip shouldn’t have happened. He’s a former federal lawman, after all. Mr. Klein once told Mr. Stern: “Giving schools ‘leadership’ or ‘social justice’ themes is fine with me, as long as the teachers and principals do not bring politics and ideologies into our classrooms.” The time has come for the chancellor to stand and deliver before the situation spins further out of control.