What a library! You want a rabbit, a snake, or a. . .?

Mandy Gardiser, an elementary pupil at Cajon Park School in Santee, arrived at the library, clutching her library card.

Her excitement gleamed as she held a rather unusual conversation with librarian, Doug Kaye, that went something like this:

''Both rats are checked out,'' said Mr. Kaye. ''Would you be interested in a rabbit? This is Sniffles, the French lop rabbit.

Mandy, dressed in a crisp orange dress, fidgeted with her card, shyly pushed back her blonde locks, and peered into Sniffles's cage and then down the line of cages on the library shelves in Room 10.

''Mama said to pick one out, but don't bring a snake home,'' she said.

That left Rosy, the boa snake, for another library card and another time.

Mr. Kaye pulled Sniffles out of his cage. But Mandy Gardiser had other plans. Moving over to the cage by the door, she stared at Tweety, the parakeet, and proceeded to check him out.

Welcome to Cajon Park School's pet library, where for good achievement and citizenship, a pupil can cuddle an animal or take it home to enjoy over a weekend.

Instead of books, the shelves are lined with animal cages.

Operation of the pet library is relatively simple. Animals go home with students on Thursday and are returned on Monday. Along with the critter, students also check out its food, courtesy of the library.

Before an animal can be taken home, a parental-permission slip is required and instructions on the animals are provided. To interpret the instructions and to provide the required care is up to the students -- and the sense of impending responsibility is good for them according to the pet librarian.

In the pet-library inventory are Sniffles, the aforementioned French lop rabbit; Bucky, a black rat; Rascal II, a hamster; Rosy II, the boa snake; Tweety , a parakeet that whistles; Tweet, another parakeet; Sebastian, a kangaroo rat; and several doves.

There is a high turnover rate at the pet library. The 926 students at Cajon Park School can earn ''animal-affection points'' that can be traded for time with an animal of the student's choice.

''Animal-affection points are cards with the pictures of the animal, bearing its name and the number of minutes (from 3 to 10) that a child can hold the animal,'' Mr. Kaye explained.

Points can be earned for good classroom behavior, achievement, and academic work.

It is a method devised by pet librarian Kaye, a fifth-grade teacher at Cajon Park School. This creative teaching approach was approved and instituted in the school's curriculum in 1971. Mr. Kaye has been using it ever since. ''I'm glad we have a school system that lets me do this,'' he said.

Kaye, boyish with sandy brown hair and mustache, holds a master's degree in human behavior from United States International University in San Diego, Calif., and one in social science from California Western University, also in San Diego. His master's thesis topic comes as no surprise: ''People Behavior and Animal Affection.''

The pet library was born accidentally when a student in 1971 brought a wounded pigeon to class. Kaye, who had raised pigeons as a boy, decided they should nurse the bird back to health. As the bird improved, others were brought in that also had ailments. Then came rabbits, parakeets, sparrows, rats, hamsters, guinea pigs and other animals.

The menagerie grew to 30 animals and an elective course called ''environmental living'' was offered to 7th and 8th graders.

The elective was basically self-motivated, Mr. Kaye explains. ''Some pupils built cages and enclosures; others did research on a particular pet or species. The artistically inclined sketched animals or pursued animal-inspired poetry or short stories. Pupils could research almost any aspect of an animal, or an animal-related topic, as they pleased.''

The children recorded births, deaths, and funny moments in diaries. They noted personal experiences with the animal when on weekend visits to their homes , and this encouraged creativity and interest. The children gained insight into animal care and concern, love and respect.

In science classes ''classification of animals'' was taught. Mammals, reptiles, amphibians, birds, fish - all were studied and researched.

Kaye feels the most important part of the pet curriculum is the animal demonstration through which animal-affection points and library cards are earned. To earn animal-affection points, pupils in Kaye's class do research, then lecture on a particular animal. Afterward the listeners are asked questions. Correct answers earn animal-affection points, a library card, and time with an animal.

Any questions that remain unanswered following a demonstration require the student who deliveres the lecture to do further research.

The idea of taking a pet home for the weekend was a logical and natural development. During the week most of the animals were in cages -- or in children's arms -- but someone had to take care of the animals over the weekend. Thus the animal library idea was born.

Children in grades four through eight on Thursdays, if they have a permission slip signed by a parent and a library card, can check out a pet for the weekend.

On the checkout day, the animal is delivered to the student's room with his food. The student is given a briefing on what to do to make the animal's visit a pleasant one.

The animal library has proper sanitary conditions, maintained by monitors who spend their free time caring for the animals, feeding them, cleaning cages, and acting as ''librarians'' on checkout days. In addion to regular cleanup times, the volunteers check food, water, and cleanliness each day. Once a week a crew of four monitors with the assistance of the school custodian cleans the floors of the classroom.

But, does the screech of animals distract the class?

Not really. Kaye feels that discipline problems decreased with animals in the classroom - a feeling Cajon Park Principal Betty Bodge seconded:

''It creates a feeling of pride and sharing some individual academic skills, '' she said. ''It's pride in something living. It doesn't interfere with the curriculum of individual children, and they handle it well.''

Parents, children, and the PTA and teachers are enthusiastic about the program and annually hold a fund-raising event to keep it going. Animal Week, held the second week in January, features guest lecturers; animal demonstrations by students; and art, writing, and photo contests with animal themes.

''Funds for the animal library are used to purchase animal food, first-aid and sanitation supplies, new cages and aquariums, new animals, and new animal pamphlets and books,'' Kaye explained.

In addition to Animal Week, library funds come from newspaper drives, PTA projects, and aluminum can collections.

In the end, it all goes toward learning. Or, as one sixth grader expressed it , ''We have to feed them -- learn how to take care of them. We're learning by doing -- not from a book.''