Miriam Geller was 55 and a teacher with 11 years' experience when she began a new job at the Bugbee Elementary School in West Hartford, Conn. After her second week on the job, Geller was told she was being replaced -- by a 27-year-old woman with three years' experience. Geller sued.

In going to court, Geller did what an increasing number of Americans are doing successfully these days -- she charged the West Hartford school system with discriminating against her on the basis of her age. Six years later, Geller had won and the school system was forced to abandon a policy that the court ruled was illegal because it effectively barred older teachers from obtaining jobs in West Hartford.

Age discrimination cases, a rarity 10 years ago, have become a major area for litigation in the burgeoning field of employment discrimination cases -- rivaling race and sex cases. A number of such suits are being won, forcing employers to reexamine old assumptions and practices. At the same time, though, some critics complain that Congress has established contradictory goals, putting employers in a straitjacket at worst or forcing them to choose between the conflicting priorities of race, sex and age.

In the two years since the federal Equal Employment Opportunity Commission took over age discrimination cases from the U.S. Department of Labor, the number of complaints filed has more than doubled-- from 3,097 filed in fiscal 1979 to 8,779 in fiscal 1981. The commission filed 89 suits last year -- the largest number since Congress outlawed discrimination based on age in 1967.

Many more cases are settled out of court by the commission. Age discrimination cases now account for roughly a quarter of all the work done by the commission, which also is responsible for investigating and seeking court remedies where necessary in race and sex discrimination cases.

The federal Age Discrimination in Employment Act of 1967 prohibits employers from discriminating against a person in employment, compensation or working conditions on the basis of age. The act was amended by Congress in 1978 to cover persons between the ages of 40 and 70, effectively raising the mandatory retirement age from 65.

Geller's experience in facing discrimination because of her age was not unusual. The older person applying for a job often encounters a number of subtle and not so subtle impediments. A 67-year-old lawyer, for example, who had a series of frustrating experiences while looking for a job listed a number of reasons employers will give for not hiring an older applicant. "They'll tell you there's a freeze on or that you're over qualified. There's all sorts of doors slammed in your face. They won't tell you, but they don't want an older person working there."

Sara Deane, a 62-year-old with a master's degree, described her own growing frustration at finding a job appropriate for a woman of her education and experience. After taking a leave of absence from a teaching job in the late 1960s to work toward a doctorate, Deane found that she had lost her job because of a local surplus of teachers.

Most recently, Deane took a year-long course to train to become a paralegal employe in a law firm. When she heard that a "large and very elegant law firm" in Washington was looking for four paralegal workers, she sent in her resume, which does not give her age, and was called in for an interview, she said. Actually, she was called twice, she said, since another person in the law firm saw her resume and also asked her to come in but withdrew the invitation after learning that Deane already had been interviewed by someone else in the firm.

"If my qualifications were impressive enough to get two calls from the firm," Deane said, "that clearly indicates that I was considered qualified for the job. But when I showed up as an older person, I was not qualified for the job. As an older person, I'm not supposed to be able to learn."

In her present circumstance, with her unemployment insurance about to run out, Deane said, she has begun considering work that she previously would have spurned. "I am very discouraged," she said. "Rejection is now cycled into my presentation of myself. I now expect to be rejected even when I psych myself up before an interview."

Geller, who the court found had been denied a job on the basis of her age, offered to accept a position at a lower pay scale than she was in fact entitled. During the time she was looking for a job, she said, "I came across several people who were in the same position I was. They were usually older people, people past 40. And they would say, 'Oh, that's the way it is.' " Some of them, experienced teachers who had left their profession and were seeking to return to it, she said, had to settle for jobs as substitutes, jobs that paid no more than $20 a day -- when they could get work at all.

When Geller thought she had a full-time job and then found it had been taken from her and given to a younger, less-experienced person, she said, "It got my dander up . . . While I've never been much of an activist before, I was angry enough about this that I wanted to do something about it."

Gladys Sprinkle, director of the nonprofit, Chevy Chase-based organization, Over 60, which finds jobs for persons 50 and older, described her experiences in placing older job applicants. "I've been sitting at this desk since before they had age discrimination laws," she said. "I could hear them say,'Don't send anybody over here who can't stand behind this counter all day.' They don't say anything now. They'll see you now. They're beautiful. But nothing happens."

As the law becomes more refined and potent a tool, and as employers become more aware of it, more subtle practices are being adopted to discourage older job applicants, according to several persons interviewed. One technique is to screen out older applicants by having them call for a job interview appointment. The caller will be asked a series of questions, including a description of his or her job experience, high school graduation date and other relevant information. Without referring to age, the interviewer will then inform the caller that jobs are not available for someone with his or her credentials. The critical question asked was the high school graduation date, but age was not directly mentioned. This approach by the employer screens out older applicants, leaving no record or statistical evidence that they ever were interested in the job.

Prospective employers may also schedule job interviews on college campuses, where an older person might feel uncomfortable standing in line with much younger applicants. Or, an employer might advertise a position without using the company's name, inviting applicants to send their resumes to a post office box. Resumes from older applicants are simply discarded by the employer and the applicant has no easy way of knowing who the potential employer was.

"Hiring cases are the hardest to prove unless the employer has an admitted policy of not hiring older applicants," said Daniel Williams, counsel for age discrimination for the Equal Employment Opportunities Commission. Employers, he said, have become more guarded about rejecting older job applicants. "They don't put a red circle around the date of birth and leave the record lying around anymore," he said.

The bulk of the cases being brought to court and won by frustrated older job applicants involve layoffs or firings, according to Williams. These cases are easier to win, since a clearer record and basis of comparison exists.

Geller's case was unusual in two respects. It involved a pattern of discrimination in hiring rather than in layoffs. And the issues in her suit were presented with uncommon clarity. The school system contended that it was not discriminating against older teachers, but rather had adopted -- as a cost-saving device -- a policy of not hiring new teachers with more than six years' experience. Geller's lawyers were able to prove that that policy had a disproportionate impact on persons 40 or older, the group protected against age discrimination by federal law.

The federal age discrimination law does exempt certain categories of workers from its provisions. "Bona fide executives," persons in high policy-making positions and persons holding jobs with unlimited tenure may be compelled to retire when they reach 65. Certain jobs may be designated as carrying a "bona fide occupational qualification" where age may be taken into consideration. If challenged, however, the employer must be able to establish that age is a legitimate consideration.

Precisely what the law means still is being defined, according to a number of lawyers active in employment discrimination cases. One court ruling, for example, held that applicants seeking jobs as bus drivers could be rejected on the basis of age if they were past 35. On the other hand, a U.S. court in California ruled last May that two airline pilots and a second officer who sought to continue working past their 60th birthdays could not be forcibly retired. The pilots won the right to voluntarily downgrade themselves from their former positions to the lesser status of flight engineer, a position that the court ruled did not carry a bona fide occupational qualification allowing mandatory retirement at 60. In several other cases where employers have tried to use age as a bona fide occupational qualification, courts have ruled against them.

The bulk of the cases have involved layoffs. When a pattern can be established that an older worker has been singled out for special treatment on the basis of his or her age, courts frequently have ruled that the layoff violated the law. In cases involving individuals, employers are finding that former practices and policies no longer can withstand a court test. Companies that attempt to cut costs by laying off older, higher-paid executives while retaining younger, lower-paid employes may find themselves paying substantial money damages to their former employes. Juries across the country have recently awarded damages of $100,000 and more to aggrieved older employes.

Some lawyers with experience in employment discrimination cases see conflicts developing between race, sex and age considerations as the economic crunch forces employers to cut back. One lawyer described a situation in which an employer, concerned about retaining black and females employes hired under affirmative action programs, wound up dismissing a disproportionately high number of older employes -- an almost inevitable result if the least-senior employes cannot be laid off. On the other hand, if an employer tries to avoid age discrimination complaints by honoring seniority in laying off workers, he may find himself brought into court for sex or race discrimination.

Gerald P. Norton, a lawyer who represents employers in discrimination cases, said he sees "tension between the age act and the civil rights acts." Norton's colleague, Walter B. Connolly Jr., went a step further to say that it is "imperative that the Age Act be amended, because I think it is out of step with the other civil rights acts."

Connolly, who also spends a substantial amount of time advising and defending employers in discrimination cases, characterized many age discrimination cases as being brought by "people who have had the advantage of discrimination all their lives (who) are now claiming that the people coming behind them are going to hurt them."

In order to steer employers through the difficult channels posed by the various laws Congress has enacted, Connolly said, the first thing he advises them is that "they have to have an objective assessment system for employes. Most employes are rated above average to outstanding because most supervisors take the path of least resistance because they don't want to deal with the limitations of their workers."

Connolly said he tells employers, " 'You have to set up an assessment system that is candid, brutally candid, because the day may come when you're not going to want to promote someone or you're going to intend to lay off someone and you're going to have to live with the results of your assessment system.' "

Monte B. Lake, a lawyer who also specializes in employment cases, said that his firm now advises clients not to have questions concerning age on their employment application forms. According to Lake, the problem of age discrimination litigation is at least partially one of education. "So often," Lake said, "you'll get a gratuitous comment from a supervisor that's age-related and it's things like that that trigger litigation -- comments like, 'We need some new blood in here.' " Such comments, according to Lake, followed by a firing or layoffs, invite litigation.

Connolly said he also advises employers who have laid off a sizable number of workers to institute a limited hiring freeze afterward, allowing only persons with specialized skills to be hired.

As for the time-honored use of "over qualified" as a reason given not to hire an older job applicant, Connolly said, "I wouldn't use that as an excuse." Acknowledging the usual reasons given by employers for not wanting to hire an older person whom the employer may consider over qualified, Connolly said, "If I were confronted with that situation as a lawyer, I would tell them to hire that person . . . for legal protection."