In times of war, school officials said, teachers needed to rally behind the national cause. The letter to Wilson "could give an opportunity for unpatriotic statements," a New York superintendent explained. "There are some assignments in the world that are not proper for a classroom in a public school, and this is one of them."
And if you think teachers today are free to critique our own wars, you're wrong. As America prepares to commemorate the 10-year anniversary of the Sept. 11, 2001 attacks, indeed, its teachers are arguably less free than at any time since the 1960s. And that should worry anyone who cares about the values that we celebrate on 9/11 itself: human liberty, justice, and freedom.
Consider the fate of Deborah Mayer, a middle-school teacher in Indiana. During a lesson from a student current-events magazine about the war in Iraq, her students asked her if she supported the war; Mayer said she did not. When parents got wind of the discussion and complained, the school district refused to renew Mayer's contract.
And in 2007, a federal circuit court upheld the district's decision. "Expression is a teacher's stock in trade, the commodity she sells to her employer in exchange for a salary," the court said. "A teacher hired to lead a social-studies class can't use it as a platform for a revisionist perspective that Benedict Arnold wasn't really a traitor, when the approved program calls him one."
So if the "approved program" says that the war in Iraq - or in Afghanistan - is a good idea, the teacher can't question that, either.
Indeed, the teacher can't question anything. She's simply a paid ventriloquist, echoing the pieties we put in her mouth.
And that's been the case for most of our history. During World War I, San Francisco fired a teacher for telling his class about anarchism, which the school board called a "contravention" of "true Americanism." In Chicago, another teacher was dismissed for using a picture of the Kaiser in a German conversation lesson.
In World War II, when the nation fought a racist enemy abroad, schools often blocked any discussion of prejudice at home. "The most dangerous subject right here is the colored race," a white teacher told an interviewer. But in wartime, another teacher admitted, any controversial topic could get him in trouble. "If it touches the community deeply, they won't let you present both sides," he explained.
Nor could teachers "present both sides" during the Cold War, when America faced off against a new foe: the Soviet Union. Schools provided teachers with lockstep curricula that detailed the evils of the USSR and communism. Those who deviated from the script - or who tried to provoke a real discussion about the subject - came under suspicion as communists themselves.
Teachers gained a bit more freedom during the 1960s and 1970s, when they taught lessons about civil rights, the women's revolution, and the Vietnam War. Courts also provided them slightly more protection, reinstating a Texas teacher who had been fired for exposing the pseudoscientific nature of race in his social-studies classroom.
But even during its supposed heyday, truly open discussion was the exception rather than the rule. And it became even less common in the 1980s and 1990s, when the courts began to scale back teacher rights.
Today, in light of the ruling against Deborah Mayer, our teachers have virtually no free-speech protections at all.
To be sure, the best teachers have always taught their students to probe, question, and think. And on Sept. 11, they'll do it again.
Who attacked us, they'll ask, and why? What did we do in response? Did we do the right thing? And what should we do now?
But they'll do so at their peril. And many other teachers will remain mute, or will simply repeat platitudes about America as a land of liberty. Our restrictions on teachers contradict that ideal, echoing a tragedy with a very deep history. Let's see if we can use this anniversary to change it.
Jonathan Zimmerman teaches history at New York University and lives in Narberth. He is the author of Small Wonder: The Little Red Schoolhouse in History and Memory (Yale University Press).