WASHINGTON (AP) _ In the feminist ''dark ages,'' schoolgirls and sports rarely mixed, women couldn't hold ''men's'' jobs, and Louisiana husbands controlled all money and property in a marriage - even if their wives had earned the money and bought the property.

Those were some of the problems women faced in October 1970 when the National Organization for Women formed a Legal Defense and Education Fund to challenge such ''Jane Crow'' policies.

In 15 years, the fund has left its stamp on virtually every major development affecting women in education, employment and family life - starting even before its formal incorporation with a landmark case that revolutionized the role of women in the work force.

Lorena Weeks of Wadley, Ga., had worked for Southern Bell for 18 years when she decided she wanted to become a switchman - a position that paid about $100 a week more than her clerical job. But no woman had ever been a switchman, and when she applied, her application was returned.

Mrs. Weeks filed a federal suit in 1965 under the new Civil Rights Act and, aided by NOW lawyers, won the case in 1969. It took her another two years and a court order to get a $31,700 cash settlement and the job she wanted.

Mrs. Weeks retired last December. By then the telephone company had changed the title of her job from switchman to switching equipment technician.

Before the Weeks victory, ''employers could say there are women's jobs and men's jobs,'' said Sylvia Roberts of Baton Rouge, La., the lead attorney on the case. ''In effect it wiped away that stereotypical thinking. It made it possible for women to have non-traditional jobs.''

Though it is the only women's law group connected to a national membership organization and the only one with an educational as well as legal function, NOW-LDEF is far from a household acronym. But its influence reaches far deeper than its limited name recognition and its relatively small 40-member staff and $2 million budget.

''The purpose of the organization is to help the most number of women as extensively as possible,'' says Stephanie Clohesy, executive director of the fund. ''And the only way you can do that is by withholding your participation until you can work on that case that has breakthrough potential.''

To that end, the fund has been involved in watershed suits that eliminated sex-segregated classified ads in newspapers and that prohibited the firing of airline stewardesses who got married. It has challenged sexual harassment in suits brought by television anchorwoman Christine Craft and others, and plans to take on comparable worth and unfair pension practices.

NOW-LDEF also helped win passage of a law outlawing discrimination in education - including sports activities. Its 9-year-old Project on Equal Educational Rights plans to press for better computer and technical training for girls and develop programs to prevent teen pregnancy.

Along with victories in the past 15 years have come a few setbacks, among them last year's Supreme Court ruling on Grove City College. The court said only specific programs receiving federal aid must comply with equal opportunity requirements; previously, entire institutions had to comply if any portion of their operations received federal aid.

Ms. Clohesy called the ruling ''a great tragedy'' and said NOW-LDEF is lobbying strenuously for a pending Civil Rights Restoration Act prompted by the Grove City case.

''The area that continues to be the most difficult and elusive is family law,'' Ms. Clohesy said. ''Fifty states are making 50 different kinds of rules.''

Even so, laws and lawsuits since 1970 have gained for married women more equitable property rights and the ability to get credit, loans and mortgages on their own. Also eliminated was Louisiana's infamous ''head-and-master'' law.

Ms. Clohesy said progress for women seems almost ''puny'' compared to the sweeping gains of the 1960s civil rights movement, tending instead to be incremental and cumulative.

''It takes many cases sometimes to build to a great achievement. A lot of our work has been done at the state level. ... It's not like deciding one grand case at the Supreme Court level that is going to change everything for all time,'' she said. ''We would need the Equal Rights Amendment in order to do that. Without it, we are fighting piecemeal.''

''Report 2000,'' NOW-LDEF's 15th anniversary publication, notes that the group continues to monitor court activity in states that ERAs and it trains lawyers to make the best use of such laws.

''NOW-LDEF has not lost sight of the importance of an ERA. We never will,'' says the report. ''We have no doubt as we look to the century's end that we will write women's rights into the Constitution.''

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