About 1 million teen-agers become pregnant each year, but federal, state and local governments are running few practical programs to prevent pregnancy, the House Select Committee on Children, Youth and Families reported yesterday.

Because of abortions and miscarriages, about half these pregnancies -- 500,000 -- produce children. But more than half of these children are born to unmarried girls who then face years of welfare dependency because they lack financial support and often are unable to finish school and find a stable job.

"The human and fiscal costs to all are unacceptable," said Chairman George Miller (D-Calif.), in releasing a report signed by all the committee Democrats and three of its 10 Republicans.

Miller and most members who signed the main report said, "We know contraception works. We know sex education can make a difference. We know comprehensive health care is essential. And we know there are emerging prevention models, like school-based clinics, that have already shown enormous potential. This report makes all too clear that these proven and promising preventive approaches are everywhere too few, underemphasized and uncoordinated."

Miller said a survey of the states on what is being done to prevent pregnancies showed promising comprehensive programs, sometimes conducted within the schools. But he said only seven states -- California, Colorado, Illinois, Michigan, New York, Pennsylvania and Rhode Island -- are funding broad plans to combat pregnancy.

The best programs, Miller said, take place at schools and other institutions -- where children are located -- instead of ones that force them to come to special clinics. These programs involve not only girls but often male teen-agers, and sometimes their parents. They usually combine education on sexual abstinence, contraceptive information and services, programs to convince teen-agers that their lives will be made miserable by unwanted pregnancies outside of marriage. He said an adolescent clinic at St. Paul (Minn.) Central High School -- offering family planning, contraceptive counseling, a social worker and other services -- had reduced pregnancy rates over five years by 56 percent.

The Committee's senior Republican, Dan R. Coats (Ind.), and five GOP members disagreed with the report. They said the majority seemed to assume nothing can be done to stop the rise in teen sexual activity which, the minority said, appeared to be the real reason for the rise in teen pregnancy. They said contraception had been emphasized in public programs over the past generation but had not lowered pregnancy rates. The answer, said Coats, is more emphasis on the responsibility of the family to teach children the right values and discipline, including no premarital sex.