The Supreme Court said yesterday it will decide whether a federal law intended to encourage premarital chastity among teen-agers violates the Constitution by promoting religion.

Reagan administration lawyers say an April 15 decision invalidating the 1981 Adolescent Family Life Act is "deeply flawed."

American Civil Liberties Union lawyers counter that the law "authorizes the use of federal funds to subsidize religious indoctrination as a means of opposing premarital sex, abortion and birth control for teen-agers."

The high court is to decide whether Congress unlawfully promoted religion in passing the law, which allows religious organizations to obtain some of the money provided to promote self-discipline among teen-agers. Millions of dollars have been passed out under the law's provisions.

The law requires programs applying for funds to describe how, in providing services, they will "involve religious and charitable organizations, voluntary associations and other groups in the private sector."

The challenge was brought by clergy members, a group of taxpayers and the American Jewish Congress, arguing that the law violates the constitutionally required separation of church and state.

U.S. District Court Judge Charles R. Richey, while saying the law has a valid purpose, struck it down because it also has "the primary effect of advancing religion and fosters excessive entanglement between government and religion."

His ruling is believed to mark the first time any court has invalidated an act of Congress as an impermissible establishment of religion.

"The statute . . . explicitly permits religious organizations to be grantees and envisions a direct role for those organizations in the education and counseling components of {Adolescent Family Life Act} grants," Richey said.

Former senator Jeremiah Denton (R-Ala.), a prime sponsor of the law, estimated $14 million a year in federal funding is at stake.

Denton said he introduced the legislation to provide "an alternative to Planned Parenthood," which offers family planning counseling that includes the alternatives of contraception and abortion.

In the appeal acted on yesterday, government lawyers said Richey's ruling "rests on brittle legal premises."

"As a consequence," they said, "large numbers of unmarried teen-agers, some pregnant and others likely to become so, may lose vital benefits that Congress intended them to have."

Richey had ordered that no money be given to religious organizations under the program, but Chief Justice William H. Rehnquist earlier postponed the effect of that order until the government's appeal is considered.

In other matters, the court:

Agreed to decide in a Wisconsin case how difficult it should be to sue in state court public officials accused of breaking U.S. civil rights laws.

Turned away an appeal by an Alabama oil company executive ordered to pay the government about $20 million for violating federal price controls during the 1973-74 oil embargo.

Left intact a ruling that New Jersey officials say will make it more difficult to prosecute alleged drunken drivers cleared of more serious charges in traffic accidents.