PROBABLY THE BEST kept secret about being a kid is that it isn't easy. All those commercials of happy Nerf ball games and hilarious group meals at McDonald's work on young people for the same reason the thin ladies with the perfect nails sell makeup to adults. Your life may not be that way, but you sure wish it were.

For four children's authors, the secret is out, though, and they've tackled the pains of early adolescence in varied environments and styles. All four deal with children spending their particular season as outsiders, though the young people and their predicaments differ a great deal.

Motherless Alice McKinley, in Phyllis Reynolds Naylor's The Agony of Alice, has never reconciled herself to her mother's death. She is convinced that, if she could just find someone to adopt as a mother, all her problems would disappear. Her father is a great guy, and her big brother is tolerable, but all those barriers between girl and teen queen seem insurmountable without the help of a wise woman. As she writes in her classroom journal after a particularly trying day, "If I had a mother . . . I would have been a gypsy or a ballerina and none of this would have happened."

Naylor has presented a compassionate portrait of a girl's journey toward womanhood, and though the book provokes memories of Judy Blume's Margaret, Alice stands on her own as a wonderful evocation of those difficult times every 12-year-old must endure.

Quite different from the suburban Alice is Betsy Byars' The Not-Just-Anybody Family. The Blossoms are dirt-poor country people, and though the three Blossom children love their grandfather, Pap, with whom they live while their widowed mom travels the rodeo circuit, they find their lives difficult on a tangible level. Pap runs a still, and when he is arrested, the three kids, Maggie, Vern, and little brother Junior, must care for themselves.

Their shrewd and resourceful solution would make any child proud, and the touch-and-go events surrounding their adventures are exciting indeed. Their world may be foreign to most readers, but their personalities won't be, and the gutsiness of these gritty kids will please most readers.

LESS SATISFYING is E.L. Konigsburg's Up From Jericho Tel. Konigsburg has long been a favorite, and the lessons in wisdom and tolerance usually offered in her books are always welcome. But in this book she takes on a really tough topic: the essence of art. The story takes two lonely 11-year-olds, Jeanmarie and Malcolm, from an innocent bird cemetery to the underground dwelling of the spirit of Tallulah, an actress who lives in disembodied splendor beneath the earth.

Tallulah must find the mysterious Regina Stone, stolen from her neck the night she died. She sends Jeanmarie and Malcolm out (invisible thanks to the actress' magical Orgone Layer) on "assignments" which, in a way known only to her, will solve everything. "I asked you to give us a hint about how we are to do this assignment," Malcolm complains, "and you said 'very well.' I'm waiting." "That's how you're supposed to do it," replies Tallulah, "very well. I want to get these preliminaries over with so that you can find my necklace."

Though Tallulah is lovable and eccentric, and though she generates enough self-confidence in her two charges to guarantee that they will pass more easily through the outlaw period of their lives, the reader doesn't quite join the parade. As the youngsters discover the necklace, and the reason for its theft, they also watch as Tallulah's living protege's argue about the gift of talent and the penalties of "being stingy with it."

Somehow the two issues -- Tallulah's quest and those she launches for the children -- never mesh, and the lessons they learn are blurry and unsatisfying. Though wisdom from older people has often been a particular gift in Konigsburg's work, she falls short of her goal here, though the adventures en route are funny and exotic.

ALSO EXOTIC is the goal of Jamie Carr, a working-class British boy who decides, despite ribbing from his classmates, to study ballet. In Jean Ure's You Win Some, You Lose Some, Jamie does just that.

Persuaded by his wealthy ballet partner Anita that he really could make it in the world of dance, Jamie quits school to prepare for auditions at Kendra Hall, a premier ballet school. But he must prove himself not only as a dancer, but also as a man.

Preoccupied, like any adolescent, with sex, he finds it tougher and tougher to meet a girl who will respond to him. And all the issues of sexual ambiguity come crashing into his life when the first real "pass" made at him at school is made by another male student.

How the very heterosexual Jamie deals with his image problems, and his girl problems, is a touching story. Adult readers will be pleased to find the sound values of love and friendship in sexual relationships very much in evidence. The world of the British "lower crust" may be somewhat alien, but Ure deals admirably with ambition, hard work, and the more immediate issues of teenage romance as well.

It's probably still a shock to many adults to find novels for young people covering the thorny questions of homosexuality, menstruation, unjust imprisonment, and the absolute loneliness of the outcast. But when they work, they provide much-needed outlets for the current versions of adolescent anxiety and pain. The more successful of these books would probably provide a safe jumping-off place, too, for parents wishing that they had an easy way to open tough conversations with their kids. While books for youthful readers provide hours of pleasure to their young fans, parents may also find them a useful key to some of those forgotten agonies of childhood. The committed writers of children's fiction offer rare insight into the secret world of young people, a world adults, and their children, might be better off for visiting together.