A rite of passage for 2 million students each year, the exam known as the SAT can be a major determinant in where they go to college. But how fair is it? In his new book The Big Test: The Secret History of the American Meritocracy, author Nicholas Lemann traces the history of the Educational Testing Service, which has administered the two-part exam for half a century. Though the SAT was intended to offer equal opportunity, Lemann argues that it perpetuates an elitism it was meant to prevent. "People think the system is natural, like God made it," he says. "I wanted to stir things up, get people talking."

Lemann, 45, grew up in New Orleans, where his father practices law and his mother was a psychologist. He was expected to join the family firm but broke ranks in 1976 when he went to The Washington Monthly instead of applying to Harvard Law School. The author of the 1991 bestseller The Promised Land: The Great Black Migration and How It Changed America, Lemann joined The New Yorker last April. A divorced father of two (Alex, IS, and Theo, 10), he plans to marry editor Judith Shulevitz this month. Contributor Jennifer Frey spoke with him at home in Pelham, N.Y.

What are the origins of the SAT?

It evolved from the Army Alpha IQ test, which was developed and given to recruits during World War I. The Scholastic Aptitude Test, which supposedly measured innate mental capacity, was first administered in 1926. In the 1930s, Harvard University president James Bryant Conant promoted it as a democratic way to select students for university scholarships in the hope that they would become public servants. After the Educational Testing Service was set up in 1947, more colleges required it.

So the SAT is an IQ test?

I don't accept the premise of an intelligence quotient—that one can measure a physical property of the brain that's inherited from your parents. That said, IQ tests are somewhat similar to SATs. They gauge how well you read and interpret, vocabulary and conceptual skills. Not so much specific knowledge as how you think about problems. Technically, the SAT is designed to predict a student's grades during freshman year. That's all it does.

Why are you critical of the test?

There's a sense out there that test scores are a scientific measurement of one's innate worth as a human being. That's why nobody forgets their SAT scores—people internalize them for good or for ill. People believe the SAT completely determines where you'll go to college and therefore your socioeconomic destiny.

It's true that a high SAT score can put you on a track that leads to an elite university and a high-paying job. I don't want to say that SATs and college admissions are the one narrow tollbooth that lead to all upper-end roles in society. But while no school decides solely on the basis of an SAT score, it is a number that gets looked at. Colleges brag about how high their average scores are and try to get them up, almost as a marketing technique. Some employers have begun asking for SAT scores on resumes, and that's alarming.

Are families overanxious about SATs?

One thing I find horrifying is the test-preparation craze. Many high school students take the basic Kaplan or Princeton Review courses, which are relatively harmless. But there's a new tier emerging—prep-ping as early as seventh grade, hiring a $500-an-hour tutor or someone who will help write your admissions application essay for $3,000. It's a way for those with money to manipulate the system in their kids' favor.

Does affirmative action help?

It's consistent with the good intentions of the people who set up the testing system. In his early years at Harvard, Conant deliberately recruited Southerners and Westerners because he wanted a national elite. The gap in scores between African-Americans and Latinos versus whites and Asians has been consistent since there's been intelligence testing. Affirmative action is not the solution to all our problems, but it is in the spirit of Conant's ideas. You can't have a multiracial country with a monoracial leadership. All the recent debate is healthy. I think we'll end up with something short of a harsh meritocracy based totally on numbers, and that's good.

Even if flawed, isn't the SAT the best standardized test we have?

There are achievement tests such as the SAT II that predict freshman-year grades just as well. But what our country should really do is upgrade the quality of elementary and secondary public schools so they provide a reliably decent education for all. Part of that is developing curriculum standards, which is already happening in New York, California, Texas and other states. Then we can agree on a national curriculum and develop a college admissions test based on what you've learned in high school and how well you've mastered it.

Meanwhile, how can parents help their kids improve their scores?

Have them take the Preliminary SAT before they even think of doing test prep; maybe their son or daughter will do well and they won't have to go through all the rigmarole. Then they should ask themselves if their kid really wants to go into the fields that academically supercharged schools lead into, such as law, medicine and management consulting. And if kids really want to improve their odds of getting into a place like Harvard, help them develop a distinctive interest rather than just upping test scores. Even perfect scores don't guarantee admission to elite schools anymore.