Walter North is obsessed with women's dirty shirts. Sometimes, he says, he and his colleagues even would take freshly dry-cleaned ones, rub them in dirt and then return them to the cleaners. For all this, he got an A.

"Well, I think we deserved it, though it's admittedly silly at first blush," says North. Silly, sort of. But serious enough to get nationwide media attention, involve the District government and scare the starch out of the biggest trade association for dry cleaners and launderers.

 North, a night student who works by day as a bureaucrat at the Agency for International Development, and two of his fellow students at George Washington University Law School, as an exercise in their legal activism class, are the plaintiffs in a series of complaints against 27 Washington dry cleaners and the International Fabricare Institute with the D.C. Office of Human Rights.

 The trio, calling themselves the Coalition Against Discriminatory Drycleaning, allege that dry cleaners practice "sex-based discriminatory pricing," i.e., women pay more to have their shirts laundered than men. Similar suits have been brought in San Francisco, Berkeley and Los Angeles.

 The group has had enormous success. The complaint originally took on only two cleaners who happened to be close to the school in Foggy Bottom. Last week, the cleaners, Royal and Vogue, signed a document during a news conference agreeing not to charge more for women's shirts than for men's.

 Women, says North, "are tired of higher prices. The costs add up and they're an incredible detriment to women trying to establish their careers." The other students -- Sara Nichols and Heidi Halleck -- were similarly interested, considering they were just about to move from sweat shirts to dress shirts as new lawyers.

 They started the class in the fall, preparing a 100-page supplemental brief. After working with their professor, John F. Banzhaf III, they submitted the complaint to the Human Rights office in March. The document showed evidence of arbitrary pricing by two dozen area dry cleaners, including up to 200 percent more charged for women than for men. Different prices for the same "oxford-style" cotton shirts ranged from 25 cents to $ 4.60. They also used a unisex print shirt. When it was brought in by men, the lower price was charged; when women brought it in, the higher one was.

 The next day, they had a surprise meeting with International Fabricare, the Metropolitan Drycleaners Association and the Korean Drycleaners Association, who struck back with their own justifications for the prices. The most important argument centered on shirt sizes. The dry-cleaning representatives asserted that women's shirts generally were too small to fit on mechanical presses, some of which have been in use since the 1950s. "It is peculiar that automatically women were charged more -- in my 45 years in the business, I have never seen anything like that, and that is wrong," says Ed Boorstein of the Metropolitan Drycleaners Association. "But we should have freedom to price the labor involved. If a shirt takes hand work, because we can't do it on the presses, we should be able to charge for it. If we can't we won't be able to stay in business."

 The students' argument rests on the D.C. Human Rights Act, which states discrimination "cannot be justified by increased costs to business, business efficiency or comparative characteristics of one group as opposed to another." In other words, the disparate effect on one sex cannot be used to justify the differences in cost. "Size is an 'immutable characteristic,' and discriminating because of the effects or consequences of race or sex is illegal," says Banzhaf. "If the shirts have other characteristics -- puffy sleeves, rounded collars, fancy fabric, frills -- that is a matter of choice, and should cost more."

 In addition, Banzhaf points out the large discrepancies in pricing. "Since several charge the same price for shirts and are making a living, others cannot argue 'business necessity,' " he says. "And, ultimately, it's going to become a practical business matter, because they are going to need to attract women. And if they discriminate, women won't go to them."

 Banzhaf and his students plan to keep the issue visible. In early June, they filed against 25 more dry cleaners, this time asking for the city to revoke business licenses. On June 20, they dragged the International Fabricare Institute into the fray, accusing the trade association of encouraging discrimination with its 10,000 members. According to District law "aiding and abetting" discrimination also is illegal. Similar complaints may be brought against the Metropolitan and Korean Drycleaners Associations.

 The two original dry cleaners settled last Friday, agreeing to condemn sex-biased pricing discrimination, ignoring the gender of the person bringing the shirt to the store or whether it is a man's or woman's shirt, whether it buttons to the right or left, its size (unless it is unusually big or small) and the shape or cut. But Jon Hee Shin of Royal Cleaners and Uk Hwang of Vogue, both Korean immigrants who speak little English, did not admit to violating the law. In fact, their attorney Silvia Park said she hoped someone would oppose the law school group. "It would have cost them [the two dry cleaners] thousands of dollars in legal fees that they can't afford to litigate a 'hot' issue," she said. "They perceive it as a battle between David and Goliath ... they just want the media attention to go away and end the disruption in their lives."

 Banzhaf, however, told the press conference his group was going to start playing tougher. "Dry cleaners might now lose their licenses or have to repay women by free laundering of shirts for all the years they have overcharged," he said.

 Jim Mercer, the associate director of the Office of Human Rights, backs him up. "We'd like to settle the claim without a lengthy investigation, but if we have to have one, we will," he says. "I think it would be in their best interests to settle, because industry always loses control when the city gets involved."

 And, worst of all for the industry after the wide news coverage, the American Civil Liberties Union is threatening similar action in Michigan, and activist groups around the country are calling the students for information. "I love what the students are doing. Three cheers," says Molly Yard, president of the National Organization for Women. "I'd tell them to please let us help, but they seem perfectly capable on their own."

 All of which makes Walter North very happy. "We showed that you can use law as an instrument for social change," he says. "This is my first legal action and the fact that it's had so many real-life implications is really satisfying."

 To say nothing of the satisfaction on the home front. "I really knew it as a success," he says, "when my girlfriend turned to me and said, 'With all these years of studying, you've finally done something.' " Suiting Up

 Though it may seem an oxymoron, sometimes law school can be fun. While working on their dry-cleaning project, one joy for the students was thinking up puns to deliver to the media. Among their choices: Don't be taken to the cleaners; this is an important suit; we have a new wrinkle in the case.

 "We want the students to have fun, get excited about public-interest law," says Prof. John F. Banzhaf III, who has been teaching the legal activism course at George Washington University for two decades. "I think you learn something best by doing it and pursuing a topic of interest."

 In 1988, the class played a key role in forcing District men's clubs to admit women members, including the 110-year-old Cosmos Club, battling its "freedom of private association" argument by pointing out that they held a liquor license, which put them under city purview.

 Other cases include getting D.C. police to arrest husbands immediately in cases of domestic violence, requiring no-smoking sections in airplanes and smoke detectors in airplane lavatories, the 5 mph bumper standard, better school-bus safety standards and getting former vice president Spiro Agnew to return to taxpayers money he received from bribes.

 The students pick their own topics and are under close academic supervision. "The costs are minimal, the legal research is free and they are their own clients," says Banzhaf. "It's sometimes harder because they don't know as much, but they make up for it in energy."

 Since grades aren't given for energy, do they have to win to get ahead? "Grades are based on quality of the legal document they turn in," says Banzhaf.

 Still, it's a thrill to win. "True, true, but any customer can do what we do. File complaints, tell your friends, make noise," he advises.

 Banzhaf and his students will continue doing all of that. Their next target, with action likely coming next semester: discrimination in haircutting prices.