Detrix Young, a Wal-Mart employee in Aiken, South Carolina, reports that she sat in a store-wide meeting where one of her female co-workers asked why the men in the store earned more than the women. One of the male managers answered that "men are working as the heads of their households, while women are just working for the sake of working." Another male manager laughed, even though several of the women were single mothers trying to make ends meet on a Wal-Mart paycheck.

Young is one of more than a hundred current and former Wal-Mart employees who submitted declarations to a federal court in support of their joint claim that Wal-Mart ? the nation's largest private employer ? discriminated against women in stores around the country, paying them less than male workers and promoting them less frequently. Later this month, the Supreme Court will hear the case to decide whether the women may bring their claims as a class action, or must bring their cases one at a time. The ACLU, along with the National Women's Law Center and joined by 32 other civil rights organizations, filed a friend-of-the-court brief today supporting the women.

In order to go forward as a class action, the women have to show that the discrimination they experienced has common elements ? that the sexist comments and pay inequity reported by Detrix Young in Aiken, South Carolina had enough in common with women's experiences in Wal-Mart stores around the country to justify hearing the cases together as one.

The evidence presented in the early stages of the case ? including the women's declarations ? shows that the archaic stereotype about women workers that Young described is also reflected in other women's accounts of how managers at Wal-Mart justified women's lower pay. In St. Petersburg, Florida, Ramona Scott reports that her store manager explained that men at Wal-Mart made more than women because "Men are here to make a career and women aren't. Retail is for housewives who just need to earn extra money." In Riverside, California, Stephanie Odle testified that her District Director of Operations explained an apparent gender-based pay inequality by saying that the man in question "supports his wife and his two kids;" her store manager in a Sacramento Sam's Club (a division of Wal-Mart) explained women's unequal pay by saying "Those girls don't need any more money; they make enough as it is." And the list goes on.

As infuriating as they are, these explanations by Wal-Mart managers for unequal pay aren't just the isolated opinions of a few sexists. On the contrary: the stereotype that men are their families' breadwinners, while women work for "pin money" is deeply entrenched, and has long been used by discriminatory employers to justify paying women less. The stereotype is not only insidious, it's increasingly untrue ? the number of women who are also the primary breadwinners for their families has risen dramatically in the past few decades, and is now about 4 in 10 mothers.

The other declarations submitted by Wal-Mart employees also reveal that outdated stereotypes were present at Wal-Mart and were used to justify inequality. One of the most common is the belief that, as Tammy Hall says her male store manager explained to another male manager in Alabama, all women should be "at home with a bun in the oven" and "barefoot and pregnant." Courts have recognized that, when this attitude is used to deny women equal opportunities for advancement, it violates the civil rights laws.

Yet when Julie Donovan, who worked in Wal-Mart's headquarters in Bentonville, Arkansas, complained to her supervisor, a senior manager, after she says another senior manager told her that she "should raise a family and stay in the kitchen" instead of advancing her career, she was told to shrug it off and have a thick skin.

Even women who didn't have families report being subjected to this stereotype, like Karla Rojas of Dallas, Texas, who attests that her District Manager suggested that she resign from her job as an assistant manager and "find a husband to settle down with and have children to relieve" her "work-related stress." And women including Geanette Bell of Pontotoc, Mississippi, report that managers assumed they wouldn't "want to be in the Management Training Program" (despite her inquiries) because they would not want to relocate their children.

Discrimination against women based on the assumption that they will not be able to perform in supervisory positions because of their presumed parenting duties is called "family responsibility discrimination," and courts and the Equal Employment Opportunity Commission recognize it as illegal sex discrimination.

Finally, many of the women report being denied opportunities to do work considered the province of men. Sheila Hall of Conway, Arkansas, states that when she asked to work in hardware, her manager said, "you're a girl, why do you want to work in hardware?" Alix McKenna declares that she was told by a manager in Lawrence, Kansas, that she could not be promoted to manage sporting goods because she wouldn't "want to work with guns." And Joanne Jaso, a single mother in Bakersfield, California, reports that her store manager refused to consider her for a promotion to a job in electronics because the job was "a man's job" that required "a lot of heavy lifting."

Perhaps it goes without saying that all of these accounts reflect the belief that women are less valuable workers than men and have no business competing for certain kinds of jobs. The courts should allow the women of Wal-Mart to establish the link between managers' stereotyped beliefs and the statistical evidence of pay and promotion disparities at Wal-Mart stores around the country by proceeding as a class action.

Learn more about pay discrimination: Subscribe to our newsletter, follow us on Twitter, and like us on Facebook.