June 19 (Bloomberg) -- Saturday will mark 40 years since the U.S. enacted a law requiring publicly funded schools to provide similar opportunities to all students, regardless of sex. It’s an anniversary worth celebrating.

Title IX, as the legislation is known, has improved the lives of women more dramatically than even its most ardent supporters could have imagined. In particular, the most controversial provision -- giving girls similar sporting opportunities to boys -- has highlighted how extracurricular activities such as sports can shape who we become as adults.

Most debate about Title IX has focused on the high-profile, big-spending world of college athletics. Such arguments miss the point of Title IX, which is to create equality in our school system, and misconstrue its true legacy -- enabling mass sports participation for girls long before college.

There are almost fifteen times as many high-school intermural athletes as in college. Before the law, almost all those athletes were male. Only about 1 in 20 girls was an athlete. By the time the law took effect -- a process that dragged on for six years as Congress fought about whether to exclude sports -- almost 3 in 10 girls were playing (see chart). Girls’ participation then remained roughly stable until it rose again in the 1990s when enforcement of the law increased.

Boys’ Programs

Critics often claim that these new opportunities for girls came at the expense of boys. Yet the data don’t bear out that claim. About half of high school boys participate in sports, and this rate has been roughly steady for the past four decades.

Boys’ wrestling programs are often portrayed as victims of Title IX. True, they have declined since the law was introduced. The motivating factor, though, is soccer, which has grown enormously in the decades since Title IX was passed and quickly replaced wrestling as a popular sport for boys throughout the country. Overall, more male high school sports programs expanded than shrank after Title IX. Tennis, cross-country and golf have all grown substantially.

Boys may not have suffered, but what did girls gain? The law’s legacy goes far beyond having fun on the playing field. High school athletics confer substantial economic benefits that last throughout participants’ lives. When one compares people with similar educational opportunities, family backgrounds, measures of intelligence and self-esteem, the annual wages of former athletes are, on average, 7 percent higher than nonathletes. Similarly, athletes get almost half a year more education than nonathletes. The gains occur equally for girls and boys.

Sports develop and reward a lot of skills that are valued in the workplace: discipline, good-natured competition, teamwork, ability to engage with adults and a diverse set of peers. Skeptics, though, will note that correlation is not causation. It’s possible that whatever makes people become athletes also makes them more successful in life, whether or not they ever set foot on a playing field.

Ideally, we would want to measure the effect of sports by running an experiment in which we randomly assign some children to participate. Title IX provides something similar to this -- a natural experiment. The law went into force simultaneously in all states, but its impact differed. In North Dakota, where many boys played sports, the demand for equal opportunity led many girls to take up sports. By contrast, in South Dakota, far fewer boys played, and so the law led many fewer girls to start playing. As a result, the law blindly selected some girls to have greater athletic opportunities based solely on where they happened to live, not on any other qualities that might have drawn them to sports.

Career Advantages

In those states where Title IX led to the greatest expansion in female sports, the post-Title IX generation of women enjoyed more education, employment and higher wages than their pre-Title IX forebears. They were also more likely to enter previously male-dominated professions such as law, accounting and even sports.

The great social experiment of Title IX proved that high-school sports participation is an important part of our curriculum. The research showed that athletic opportunities played an important role in the educational and labor force gains made by the women going to school after the legislation.

Unfortunately, we haven’t outgrown Title IX. Less than half of all athletes are girls, and the gap is larger in states where support for the law is weakest and sexist attitudes are most prevalent. Not surprisingly, these are also the states with greater gender disparities in the classroom, with boys doing better in math and science.

It’s in all our best interests to keep narrowing the gap. When we deny the benefits of sports to our children, of either sex, we limit their ability to enjoy success not only on the sporting field, but also in the marketplace as adults.

(Betsey Stevenson and Justin Wolfers, both professors at the University of Pennsylvania’s Wharton School, are Bloomberg View columnists. The opinions expressed are their own.)

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To contact the writers of this article: Justin Wolfers at jwolfers@wharton.upenn.edu; Betsey Stevenson at betseys@wharton.upenn.edu.

To contact the editor responsible for this article: Mark Whitehouse at mwhitehouse1@bloomberg.net.