VERY FEW adults would argue with a children's book whose story might help kids decide to Do the Right Thing. The old McGuffey readers did that all the time. But to be able to write for young people and communicate a message without condescension or cliche' is a rare skill indeed. Four new books for young readers make this effort, and succeed to a surprising degree.

Two veteran writers of fiction for young readers are most successful: Phyllis Reynolds Naylor in Beetles, Lightly Toasted (Atheneum, $13.95; ages 8-12) and Ellen Conford in The Things I Did for Love (Bantam, $13.95; ages 10-16). Though written for somewhat different ages, they both take original and very funny paths toward a truth worth learning.

Andy Moller, Naylor's hero, lives on a farm in Iowa. He loves farms and farming and the extended family which surrounds him-all except his rival cousin Jack. There's only one thing that obsesses Andy more than the fact that Jack always seems to beat him at everything: Andy wants to get his name, and his picture, in the local paper: "Andy had never seen his name in print and certainly not his picture. He hadn't even made the newspaper the day he was born; the hospital had mistakenly left his name off the list of babies born that week. He just had to win this contest; it was only right."

"This contest" is one held every year. Members of the fifth grade class at the local school are invited to write an essay on an assigned topic. The winner gets $50 and the check is presented at a ceremony covered by the local paper. This year, the subject is "conservation."

Andy dreams up an original, and totally yukky, method of conserving food. He also finds a way to make sure that his efforts are accurate; he uses his unwitting family and friends, especially Cousin Jack, to test his theories. And he wins. Unfortunately, his victory means that his experiments are revealed. It is not disclosing too much to say that the book's title, Beetles, Lightly Toasted, offers a hint of just what his family and friends have been testing.

Steffie Kasdan has a different problem. Another one of Ellen Conford's wonderfully honest teenage narrators, she is the heroine of The Things I Did For Love. For Steffie the mysteries of love are so intense that she decides to devote her junior psychology project to the question "Why Do Fools Fall In Love?" Fortunately for the reader, and ultimately for Steffie, she learns more than she set out to, and so do we.

At first, to an adult, the portrait of a tall blonde adolescent who doesn't understand that she is beautiful and keeps trying to bring out the "short person inside" may strain credibility -- but only until that adult remembers how it felt to be 16. Conford is terrific at evoking those days of uncertainty, the tension that develops between even the best of girlfriends when one friend is successful with boys and the other is not.

Steffie's dilemma is a bit different from the usual, though, despite her insecurities. When her brilliant best friend Amy falls for Farley the biker -- a high school dropout with a Mohawk -- Amy pushes Steffie to go out with Farley's friend Bash. Bash is gorgeous, sort of the way James Dean was gorgeous, and seems to be in the same kind of pain. We all get ready for some horrible outcome as Steffie begins crashing around on the back of Bash's bike.

But Bash, it turns out, has an older brother, Nathan, who went to Harvard; Bash's decision to quit school, he explains to Steffie, was his way of giving up trying to compete with his brother. As Steffie realizes she cares for Bash, her awakening sexual feelings are carefully reined in by the considerate young man. "I was in love with him," she tells us. "'What's more important than this?' I reached over to hug him . . . 'Right now, nothing,' he said gently. 'But when you come up for air, you start to think.' "

What Bash asks of Steffie is that she indeed "come up for air" and decide, before he falls in love with her, if she really wants him, "because I saw the look on your face when I told you I was a dropout." It takes some time, but Ellen Conford allows the two to reach a mutually helpful accommodation.

Still, as Steffie writes in her psych report, "I believe there is no single answer to the question, "Why Do Fools Fall in Love?" Everyone has his or her own individual reason. These aren't necessarily rational or thoughtful reasons, but all the data indicate that there is absolutely nothing rational about love."

IN VICTORIA Whitehead's The Chimney Witches (Orchard Books, $11.95; ages 8-12) the heroine, Ellen, must also deal with the irrational, but her dilemma is complicated by the supernatural world that seems especially visible around Halloween. In the process, she makes a new friend, one even more exotic than a high school dropout in a black leather jacket. Ellen's new pal is a witch -- or at least the son of one, and he and his mother have moved into the world behind Ellen's bedroom chimney.

Rufus is dying to be a real witch. To do that, he must produce spells that prove he is worthy to receive the Medallion of Middle Magic. One day, though, while practicing with his uncle's Medallion, Rufus goofs and sends the treasure through the chimney into Ellen's room.

Like Peter Pan's shadow, the Medallion of Middle Magic becomes the catalyst for a meeting of two worlds and the adventures such a meeting is bound to produce. Ellen, who dreads the day her brother will pass his music exam and leave home to go to music school, demands a wish before she will return the Medallion. She's going to wish that he fail the exam and stay home with her. Will Ellen make her wish? Will she survive her sojourn to the witches' kingdom on the other side of the chimney? Will Rufus get the Medallion in time to prove himself a worthy witch? In wonderful and exciting succession all these questions are answered and, appropriately for a story with witches and magic, everyone seems to live happily ever after.

Less successful, but a sweet and decent tale nonetheless, is Thomas Rockwell's How to Fight a Girl (Franklin Watts, $10.95; ages 9-12). Billy Forrester is kind of a devil, but he did eat 15 worms on a bet -- and used the money he won to buy a trail bike. So it's only fair that he get to show off with it. Sometimes though, he goes too far -- and his comrades Alan and Joe have about had it.

Hoping to discredit Billy and force his mom to confiscate his bike, they hatch a complicated scheme with some girls in the neighborhood. When Billy unknowingly befriends Amy Miller, one of the girls in the "plot," things get dicey. Amy develops serious second thoughts about her role in the Defamation of Billy. Billy realizes that maybe girls can be good companions. And Amy is stuck.

When her co-conspirators learn that Amy's loyalties are split, they plan an especially dastardly revenge. They'll pretend to be Billy and Amy and get into all sorts of trouble in disguise -- and Billy and Amy will be blamed.

The plot line is sound enough, but Thomas Rockwell has trouble deciding whether to be serious and instructive or funny and instructive. As he wobbles back and forth the book loses some of its flow. Even so, the characters are sufficiently attractive that the book will probably prove quite as popular with young readers as Rockwell's earlier How To Eat Fried Worms, and its ultimate lesson is a sound one.

Though these four books differ widely, they share a concern with the conflict between right and wrong -- and a sense of humor and compassion in dealing with moral issues. Even better, these goals are accomplished without giving the reader the sense that he's reading a morality play. Nobody ever said that Doing The Right Thing couldn't be fun. :: Cynthia Samuels is a producer on NBC's Today Show and is the author of "It's A Free Country! A Young Person's Guide to Politics and Elections," forthcoming in March.