The federal government may have finally come up with a way of forcing American parents to do something they have assiduously avoided since the nation's founding, namely, discussing sex with their children. In one of his last acts as secretary of the Department of Health and Human Services, Richard S. Schweiker announced he was going ahead with plans to require federally funded family-planning clinics to notify the parents of teen-aged girls who receive birth-control prescriptions. This, I have to tell you, makes me eternally grateful that my current teen-ager is a son and not a daughter.

The notification is to come by certified mail within 10 days after the teen-ager gets a prescription for a diaphragm, pills, or an intrauterine device. Consider what might happen to your average American family headed by, let us say, Gail and Harry Jones, parents of Harry Jr., 14, and Jane, 16, when the postman (presumably without changing expression) delivers a certified letter from the local family-planning clinic.

"Dear Mr. and Mrs. Harry Jones:

"In accordance with provisions of Title X of the Public Health Services Act, you are hereby notified that on Jan. 12 your dependent, Jane Jones, applied for and received a birth-control prescription at the above-named federally funded clinic."

Gail frantically starts to dial Harry at work, then thinks better of it and decides to show him the letter that night. She is worried sick.

"What did I tell you about that boy?" yells Harry, shaking the letter in Gail's face. "I knew from the moment I laid eyes on him he was no good. Obviously, you'll have to forbid her from seeing him."

"She'll do it anyway," says Gail.

"You're going to have to have a talk with her," says Harry.

"About what?"

"About sex," yells Harry. "And morals."

"I have," says Gail, defensively.

"When?"

"When she was eleven. Plus she had sex education in the ninth grade."

"Yeah, and look at the results."

"You can't blame this on sex education, Harry. Blame it on that little creep."

Harry and Gail sit pondering the situation in the living room.

"You've got to talk to her," says Harry at last. "You're her mother."

"She'll tell me about the bomb. That's her answer for everything."

Harry shakes his head. "I can't believe it. My little girl. How could she?"

Suddenly, Jane appears in the living room. Quickly, Gail hides the letter. "Hi, Mom. Hi, Dad. What's up?" Jane gets a box of cookies out of the kitchen and disappears into her room.

"Why didn't you say anything to her?" growls Harry.

"You have to bring these things up delicately. Anyway, I don't know what to say to her."

"Tell her to stop seeing that boy, that's what you say to her. Tell her she's too young to get involved, tell her it's unhealthy. Tell her she's supposed to wait till she's married."

Gail raises an eyebrow, is about to make a remark, then stops. Finally: "It's a sign of trust, you know."

"What is?"

"This. She knows the clinics have started notifying parents. People were even claiming that girls wouldn't go there anymore because they were afraid their parents would find out. She went anyway. It's a sign that she trusts us to have adult reactions."

"I'll tell you from adult reactions," snarls Harry. "I'll kill him."

"Harry, at least she's taking precautions. If we forbid her to see him, she'll just defy us. If I show her this letter, she'll have a fit and accuse us of invading her privacy. The best thing to do is to say absolutely nothing to her about this and hope he'll move away."

The phone rings. Jane breezes through the living room on her way to answer it. "What are you two talking about?"

"Nothing," Harry and Gail answer in unison.

Gail reaches a comforting arm toward Harry. "At least we won't have this problem with Harry Jr." she says. "He may get involved, but at least we won't have to know about it."

"That's a relief," sighs Harry.

Gail shakes her head pensively. "You know Harry, when we voted for President Reagan, I never thought the result would be that we'd get this kind of letter about Jane."

Harry turns on the television. "It's hard enough bringing up kids these days without this," he says. "Somebody ought to tell the great communicator that there are some things parents just don't want to know about."