ONEAL GIVES US the agonies of a poor little rich girl, Byars the trials of a poor little poor girl, and both write well while doing so.

In The Night Swimmers , Retta has been thrust into the role of head of the family (in her early teens) by the death of her mother in a plane crash two years earlier. Her father, Shorty Anderson, is an amiable small-time country-western singer whose one important dream is a hit recording. His widower's lament, "My Angel Went to Heaven in a DC-3," had a short say as No. 37 on the charts, but the flicker of fame was fleeting and Shorty is still performing at a local dive and getting home too late to do much in the fathering line.

This leaves Retta saddled with the care and feeding of her two kid brothers Johnny and Roy, whom she loves with the hate siblings usually feel for one another in their tender years. Her care includes a good many one-course dinners (mashed potatoes with butter; peanut butter and banana sandwiches), and late-evening intrusions into the swimming pool of a well-to-do neighbor.

These revels, forced upon the boys whether they feel like swimming or not, lead inevitably to pursuit and -- if not capture -- lectures on the dangers involved. Nothing much comes of this; in fact nothing much comes of most of the incidents in the book, which is one of its many lifelike qualities. By the time Shorty's good-hearted, scruffy girl-friend Brendelle turned up I was beginning to feel trapped in still another story about a bunch of losers, and I am tired of reading about losers (when I was a boy we read stories about people who stuck out their chests and were winners). But then if both Retta and Brendelle were not winners they certainly won me over in a wind-up that was believable, realistic and more engagingly upbeat than the sterile "lived happily ever after" endings we once fell for.

It's a funny thing about money. The family that Carrie has to contend with in The Language of Goldfish are more trivial people to my way of thinking than Retta's menagerie. I'm not sure how many young adults are going to be nailed to the page by this book, but I do wish a lot of well-heeled parents would read it.

Carrie thinks she is going crazy, but no one is paying attention. To be sure, Older Sister and Self-Centered Parents aren't listening, but before long Noted Psychiatrist is listening and listening and listening, for all the good it seems to do him or, more importantly, her. Since he is a chain-smoker, his main contribution to Carrie's illfare seemed like to be bad lungs.

Carrie lives in a plush suburb near Chicago, but not near enough to suit her. She loved her childhood in Chicago and wishes nothing about it had changed. She shows talent as an artist and prizes her friendship with her high-school art teacher, but even that situation won't hold still for her. After a couple of breakdowns and endless sessions with her analyst she seemingly performs her own therapy by telling him, "I know why I got sick," but the way she has worked it out for herslef is too pat to be completely believable, and also sounds like something a competent analyst should have led her to months earlier.

Her parents, however, are all too beilevalbe. Her father is a doctor, but like many doctors he seems to be extremely limited outside his own field, and shows little understanding of Carrie's possible problems. Her mother is busy being "upwardly mobile," besides which she can't face the notion that anyone in her family could be seriously ill, especially mentally ill.

Riding home with her father, Carrie tells him about some new, abstract drawings she has done. He says, of course, "I'd like to see them sometime." She brings them downstairs when her parents are having a drink, and draws a blank: Neither of them understand her drawings, and neither tries very hard.

Says Carrie:

"'I thought you might like to see them. They're no big deal. Just an idea I had.' Suddenly she felt clumsy, as if her body had grown huge and ungainly. She leaned over the desk and gathered the pictures together awkwardly with fingers that had become thick stubs. 'Anyway,' she said 'I'll see you at dinner.'

"She looked back into the library on her way upstairs. Her father was making himself another drink. Her mother had begun again on her needlepoint, and they were already talking about something else."

My first reaction to this was a self-riteous desire to kick both of them for being parents like that, but second thoughts left me with an uneasy feeling. Which of us, at one time or another, have not been parents like that?