Seventh grade may be the most damaging year of your daughter's life. That's the inescapable conclusion from a study of 3,000 girls and boys that found that the percentage of girls who had high self-esteem plummets an astonishing 23 percent between elementary school and middle school. Twice as many girls lose their self-esteem as do boys as they enter adolescence.

The study was commissioned by the American Association of University Women as part of its effort to get the push for educational revision to pay attention to the needs of girls and to eliminate bias against girls in schools.

The study surveyed youngsters aged 9 to 15 in 12 locations across the country. It found that the loss of self-esteem in middle school continues through high school and has much more long-lasting effects on girls than on boys. By the time girls are in high school, only 29 percent say they are happy with themselves, compared with 46 percent of the boys. Girls are much more likely than boys to say they are "not smart enough" or "not good enough" for certain careers.

The survey contradicted the popular notion that peers have the greatest influence on teenagers. It found, instead, that adults, family and school have the greater impact on teenagers' self-esteem. "As they find people believing males can do things, boys end up with higher self-esteem as they go through adolescence," the report said. "The research, particularly the focus groups, shows that young women find people, including their teachers, believing that females cannot do the things they believe they can. The result is girls' lower self-esteem.

"Teachers have a special opportunity to affect the self-esteem of their female students, and by instilling confidence, to shape their interests and aspirations."

Carol Gilligan, a professor of education at Harvard University's graduate school of education, who has done groundbreaking work in studying the psychological development of women and girls, believes that women teachers are inadvertantly undermining young women, and she believes they can be turned around to become a great source of validation for girls.

Gilligan, whose book, "In a Different Voice," paved the way for much of the recent work on the different ways men and women think and communicate, heads a Harvard research project into young girls' development in several different communities, including Cambridge public schools. Her observations, shared at a conference held by the university women in connection with the report, help explain what happens to girls as they become aware of the dichotomy between what they know is the condition of women in society and what they are taught in school.

In the seventh grade, says Gilligan, girls are saying "I don't know" when only a year ago they knew the answer. "They say they are afraid to speak up. Girls reach an impasse in relationships and in fact adolescent girls often use the phrase coming up against a wall. If they say what they see, people won't want to be with them. Girls are in touch with the world, including things that are very disheartening, such as seeing their mothers working two jobs. We are all socialized to be nice and to say there is no problem. Girls are seeing there is a problem. Women ought to say to girls, yes, there is a problem but we are going to change it. We have to start to tune women's ears to the girls' voices around them. Girls are very outspoken, but at the cost of alienating the educational system, which is a huge cost.

"You could see the conflicts. We saw evidence of loss of voice, of girls silencing themselves, declaring their own experience as worthless." They began idealizing images of women and relationships.

"We saw a struggle taking place in the classroom to sustain their psychological vitality and their education. They were being outspoken. It was causing disruption. People would say she's too loud, too strident, too rude. Girls were under pressure not to know what they knew." She said they became quiet in class. Then, depression and eating disorders set in. "They were not able to stay in touch with their own feelings."

The project Gilligan heads started after-school clubs for girls and for women teachers to strengthen girls' voices, and to help teachers "respond to the strengths that are in girls. You don't have to create it out of nothing.

"Girls are responding to something real, which is the state of women in this society. It is important to acknowledge. One thing is for girls not

to feel they are alone. Real relationships are the key to girls and to women with girls in order to construct healthy ways to respond to real problems.

"Girls," she says, "do quite well until they are 11 years old. And then suddenly the ground goes out from under them."