Once upon a time, Americans did some very bad things.

Once upon a time, Americans did some very bad things. They enslaved Africans, displaced Indians, oppressed women and exploited laborers. Then the Great American Government came to the rescue.

Spurred by protest movements for freedom and equality, the government instituted changes that brought the nation progressively closer to its founding promise.

That's the theme of most American history textbooks. And it's also what offended the Texas Board of Education, which voted last week to approve a new set of social studies standards that emphasize America's timeless virtues. The current standards, one board member explained, "are rife with leftist political periods and events: the Populists, the Progressives, the New Deal and the Great Society."

And here's what most of my fellow liberals won't admit: He's right. These bursts of reform are the spine of the story that we tell ourselves, about who we are and who we want to be. When a social problem arises, we press our elected representatives to devise new laws and institutions that will make America more compassionate, decent and fair.

That's how most liberals — and, I should add, most historians — see the world. Our heroes are the champions of social justice — Frederick Douglass, Jane Addams, the Rev. Martin Luther King Jr. and so on — and the presidents who tried to put their ideas into practice: Abraham Lincoln, both Roosevelts, John F. Kennedy and Lyndon B. Johnson.

It's not an unalloyed embrace, mind you. Many of us have criticized these politicians for their errors, blind spots and inconsistencies. Kennedy takes a pummeling every few years for the Bay of Pigs, as does Johnson for escalating the war in Vietnam.

But even our disparagement of liberal icons demonstrates our overall adherence to the liberal script. In the great national drama, our leaders are supposed to harness the power of government to the principle of social justice. And when they don't, we take them to task.

Our scholarship about conservatism reflects a similar bias. Over the last few decades, historians have produced brilliant studies of Richard Nixon, Ronald Reagan and the rise of the so-called Christian right. But most of this work proceeds from the basic assumption that the right was wrong: about religion, race, the economy and everything else.

And now — surprise — conservatives are fighting back. Look closely at the new Texas social studies standards and you'll find attacks on every sacred cow in the liberal pantheon, starting with the separation of church and state. While liberals often impute the principle to the Founding Fathers, the Texas standards hold that the founders imagined America as a "Christian nation."

The new standards also reject the idea of American imperialism, preferring to call it "expansionism." They insist on the superiority of America's "free enterprise system," which will replace the prior standards' reference to "capitalism." (Capitalism, one school board member explained, "does have a negative connotation. You know, 'capitalist pig.'")

When we get to the Cold War, the new standards note that recent archival discoveries "confirmed suspicions of communist infiltration in the U.S. government." And for the 1960s and beyond, the standards advise, students should examine the "unintended consequences" of Great Society legislation, affirmative action and Title IX.

Conservatives on the Texas school board claim that these changes will simply provide "balance" to the dominant liberal paradigm. But their red-meat rhetoric says otherwise. Would these people rest easily if students — following a "balanced" discussion — concluded that the Great Society and affirmative action were really great ideas?

I think not. And the same goes for liberals, who would bridle if the students walked away from class believing that '60s-era reforms were failures. For the most part, Americans do not enter this arena to make the case for "balance." Instead, they want their side to win.

And that's the real back story of the tragicomedy that's unfolding in Texas. It's easy for coastal liberals to scoff at the unlettered rubes of the Lone Star State, who are obviously revising history to fit their present-day predilections. But that's what we all do, all the time, and then we foist these ideas on our kids.

What if we gave them multiple points of view instead? Recent history gives us a perfect opportunity to do precisely that. After the arch-liberal author Howard Zinn died in January, his "A People's History of the United States" shot to No. 12 on the New York Times paperback nonfiction list. Just behind — at No. 15 — was Larry Schweikart and Michael Allen's conservative "A Patriot's History of the United States," which received a big boost when Glenn Beck pumped it on his radio and TV shows.

So here's a modest proposal: Instead of bickering about the "correct" version of the past, the Texas school board should decree that every high school history class use both of these texts. That would teach students that Americans disagree — vehemently — about the making and the meaning of their nation. And it would require the kids to sort out the differences on their own.

Most of all, though, it would require adults to be more "liberal" in the dictionary sense of the word: tolerant, reasoned and open-minded. And we would all need to be willing to lose, of course, if our children decided that our version of history was wrong.

Will we let them?

Jonathan Zimmerman teaches history and education at New York University. He is the author, most recently, of "Small Wonder: The Little Red Schoolhouse in History and Memory." He wrote this for the Los Angeles Times.