The television casts strong images. Pope John Paul II wraps his arms around Brendan O'Rourke, a 4-year-old from San Francisco with AIDS. The camera pans the burned-out Arcadia, Fla., home of Clifford Ray and his three AIDS-infected, hemophiliac sons. It shows the sad faces of AIDS-infected babies abandoned by their drug-addicted mothers in a New York hospital.

All are children with AIDS. These images tug at the emotions of adults; for youngsters, the pictures raise complicated, frightening questions: What is AIDS? How did the kids get it? Is it "catching" in school? Can I get infected? Will I die?

"Children have a vague and global fear of AIDS," said Dr. Joe Novello, a Washington family psychiatrist. "They hear about it and they are afraid that they are going to get it."

There's no question that the risk of a child's contracting AIDS remains low. Among pre-adolescent children, only 584 have developed the disease since the first cases were reported in 1981. Most infected children had parents who either had AIDS themselves or were in an AIDS risk group, such as those who abused intravenous drugs. A few children became ill after receiving blood transfusions or treatment with blood products for diseases such as hemophilia.

No children have contracted the disease after being exposed to a child carrying the AIDS virus into a school, according to the federal Centers for Disease Control in Atlanta. Yet as in nearly every other area of American life, acquired immune deficiency syndrome is forcing schools and parents to confront difficult subjects seldom discussed with children.

Chief among them is sex, a topic many parents have approached uncomfortably with their children or not at all. Because AIDS is chiefly spread sexually, learning about sex, especially safe sex, and abstinence is the main way to prevent the spread of the AIDS virus.

But teaching children in elementary school about sex has long been controversial. "AIDS keeps pointing out the longstanding gaps in our social institutions and social systems," said Caitlin Ryan of the Intergovernmental Health Policy Program at George Washington University. "These problems {have} existed for a while; AIDS is just bringing them to light in a compelling way. We cannot afford to avoid them anymore."

U.S. Surgeon General C. Everett Koop has strongly advocated sex education, beginning early in a child's life, perhaps as early as third grade, as a first step toward laying the groundwork for learning about AIDS and other sexually transmitted diseases at a later age.

Koop's recommendation, however, has become a political lightning rod for AIDS education programs. Some conservative groups oppose sex education programs in public schools. Sexuality should be taught by the family, they argue.

Other school districts are being criticized for carrying Koop's call too far and teaching AIDS prevention to third graders, including graphic details of "safer" sex practices, which the children often are not able to fully understand.

"For young children, Koop's point of view has been distorted," said Jean Hunter, family life curriculum specialist in the Alexandria City Public Schools. "He didn't say do AIDS education for third graders. For them to understand AIDS prevention messages, they first have to understand sexuality."

For parents, there is an increasing uncertainty as to what they should be teaching their children about sex and the diseases that can be associated with sexual practices.

Some parents will respond by doing nothing, allowing the child to learn about sexuality from peers. That could be disastrous, experts say, once children become adolescents. Without adequate instruction about contraception, some will become pregnant. Without enough knowledge about condoms and safe sex, some will get AIDS or other sexually transmitted diseases.

As a result, new attention is being focused on health education programs in elementary school -- courses that teach the fundamentals of sexuality as well as the basics of disease prevention.

Since most children have heard about AIDS, it's important to discuss the disease and explain how the virus is not spread: not from toilet seats, not from sharing towels and pencils, not from shaking hands or sitting side by side.

Learning about sexuality is a life-long process that begins practically at birth, say the experts. The toughest questions begin early, by ages 4 or 5, when children start asking where they came from.

The trick, said Hunter, is to listen to the child's question and then answer it specifically but not volunteer too much additional information. If children want more details, they will ask. "When it comes to sex, we tend to over-answer," Hunter said.

Parents also must reassure children that they are allowed to ask such such questions. "The pace at which children ask questions is partly a function of how open the family is to this kind of discussion," said Isadora Hare, staff director of the commission on education at the National Association of Social Workers in Bethesda. "Children are extremely sensitive . . . If they sense embarrassment on the part of the parents, they will not ask the questions."

If children don't ask questions, parents can use various situations -- a pregnant woman walking by, an encounter on television -- to casually bring up the subject, and then as questions arise, answer them.

Another general theme, say the experts, is that the sexual messages should be appropriate for the child's age and emotional development. Some worry that children are being pushed a little too far, too fast when it comes to sex education.

Nailing down concrete guidelines, however, remains virtually impossible, said several of the experts. But there are some generalities that can provide some direction: In kindergarten through second grade, children want to know where babies come from, but they do not understand sexual attraction or sexual intercourse. The experts recommend that parents and teachers use the correct words to describe what is going on: Say the baby is in the womb or uterus, not the mother's stomach. "Kids want to know if the baby is in the stomach with all that pizza and stuff," one expert said. By third and fourth grade, most children have figured out intercourse, Hunter said. They want to know how the sperm reaches the egg. They want to understand the mechanism. "They are very concrete thinkers, but they have no idea of the feelings between a man and a woman."

Introducing the concept of intercourse can be difficult and awkward. It's also a time when education about values often coincides with information on sexuality. Said Hare: "Say the mommy and daddy love each other very much and they hug and they kiss and then the daddy puts his penis inside the mommy's vagina. It is important to put it in the context of marriage and in the context of a loving relationship."

"I ask fourth-graders if sexual intercourse is a good or a bad thing," Hunter said. "They all said bad. They believe it is something nasty. I think they get that attitude from adults who indicate that it is bad to talk about."

Said NASW's Hare: "I think if you start teaching them early, then fear is not part of it. They will not be horrified by the concept {of intercourse}." Once a child becomes an adolescent, parental control is on the wane, said Dr. Sharon Foster, a psychologist at West Virginia University. As the adolescent becomes more responsible and independent, the parent no longer commands but rather influences, discusses and negotiates behaviors.

While many families urge their teen-agers to postpone sexual activity until marriage, many teen-agers do not. A study by the Alan Guttmacher Institute in New York City found that in 1982, the latest year for which statistics are available, the average level of premarital sexual activity among white women was 43.1 percent, and for black women, it was 56.5 percent.

Many sex counselors recommend that contraceptive practices be taught to adolescents who are entering a sexually active time of life. It is also time, they say, to teach students about the risks of AIDS and other sexually transmitted diseases.

For adolescents, the message is the same as it is for adults: The AIDS virus can only be spread by intimate sexual contact or by contamination with infected blood. Infection can be prevented by abstinence from any sexual contact, the maintenance of a mutually monogomous relationship between uninfected sexual partners and by practicing safe sex, including the use of condoms and avoiding the exchange of semen, saliva and other bodily fluids.