A movement to place health and birth-control clinics in public schools, introduced in a few midwestern cities in the mid-1970s, has begun to spread nationwide in the wake of rising concern over teen-age pregnancies.

Despite vehement opposition from those who fear that the clinics will encourage sexual activity among teen-agers, the facilities have been set up in 35 schools across the country and 75 more are planned. Last month, Los Angeles became the largest U.S. city to approve a pilot clinic after a report that high school pregnancy rates dropped 64 percent in the first three years of a similar program in St. Paul, Minn.

Like controversial rules requiring passing grades to participate in high school athletics, the school-based health-clinic movement appears to be an example of experimental social programs born in communities far from Washington but converging on the nation's capital. A public hearing is scheduled Wednesday to consider placing such a clinic at Washington's Anacostia High School, and some suburban Washington communities are expressing interest, Planned Parenthood officials said.

The clinics have been established independently by various private groups and funded by a mix of public and private funds. Most of the clinics have been set up in schools serving low-income, usually predominantly black neighborhoods where teen-age pregnancy rates are highest. Most clinics require parental consent before distributing birth-control devices. Organizers say parents have offered little or no resistance and some support.

"We have allowed six months to a year for community development before we set up a clinic," said Jennifer Young, associate director of Kansas City's Adolescent Resources Corp. "We do not assume the community wants the service until we ask them."

Judith Senderowitz, executive director of the Washington-based Center for Population Options, emphasized that the clinics are designed not only to provide birth-control information and devices but to offer broad-based health care to children whose families cannot afford doctors.

"By and large, the communities that have developed this have done it without much contact with each other," she said. Her private nonprofit group added a unit, the Support Center for School-based Clinics, in April to help coordinate efforts to establish clinics in more cities.

Patrick Fagan, director of the antiabortion Child and Family Protection Institute in Washington, denounced the movement as part of a national effort to "win acceptance of teen sexual behavior." Given the clinic movement's improving organizational techniques, "I think this whole issue is the most serious fight that we will have on our hands for years to come," he said.

Lou Sheldon, California state chairman of an Anaheim-based organization called Traditional Values, opposed the Los Angeles pilot clinic as a "demolition of parental rights." He warned that students would forge their parents' signatures on consent forms. It would be better, he said, to try to encourage abstinence by noting the diseases that can be transmitted sexually.

Senderowitz said the health-clinic movement had "practically no" opposition until a controversy erupted in Chicago this year over a new clinic at DuSable High School. An article in the Rupert Murdoch-owned Chicago Sun-Times about the clinic was headlined "The Pill Goes to School," Senderowitz said. The resulting dispute led the school board to reconsider and approve, by a much narrower margin, its original decision to allow the clinic.

The publicity surrounding the Chicago opposition led to the proposal for a clinic here. Los Angeles school board member Jackie Goldberg had taught for years in low-income area high schools with high pregnancy rates. She saw a television report on the Chicago controversy and concluded that a similar program would work here.

Board member Roberta Weintraub, an antibusing activist who often differs with Goldberg, agreed to cosponsor the proposal. It was approved, 6 to 1. Lawyers are studying the proposed requirement for a parental consent form; Goldberg said case law indicates that the clinics may not be able to refuse birth-control devices to a student who requests them.

She said she and other board members were particularly moved by evidence of potential teen-age health problems not related to birth control. A clinic in West Dallas, Tex., found that up to 30 percent of its patients had undiagnosed health problems, including 100 heart murmurs.

Still, much of the interest in the clinics has been stimulated by statistics from the pro-birth control Alan Guttmacher Institute indicating U.S. girls 15 to 19 years old have a 1-in-10 pregnancy rate, one of the highest in the world. Fagan charged that this figure is distorted because it includes married teen-agers.

The St. Paul clinics, as well as others, report that a majority of patients seek help unrelated to birth control. But the St. Paul pregnancy figures have done much to sell the program. According to Ann Ricketts, administrator of the St. Paul Maternity and Health Care Project, live births to female students at schools with clinics dropped from 59 per 1,000 in 1976-77 to 21 per 1,000 in 1979-80. The rate this last school year was 37 per 1,000, compared to a 1982 fertility rate for all city residents in that age group of 62.5 per 1,000.

Rosann Wisman, executive director of Planned Parenthood in the Washington area, said she and coordinator Sharon Robinson are contacting local school officials about setting up clinics. The most enthusiatic so far, Robinson said, is Anacostia High School principal Walton Breckenridge.

Breckenridge said he will hold a public meeting at the school at 7 p.m. Wednesday to test community reaction. Planned Parenthood is seeking foundation grants to support the clinic's $150,000 annual budget. "I'm generally in favor of it," Breckenridge said, "but we will find out what people think at the meeting."