Children's poetry; Rhyme and imagery to capture kids; Knock at a Star, by X.J. and Dorothy M. Kennedy. Boston: Little, Brown & Co. 148 pp. $12.95. Poems to Read to the Very Young, selected by Josette Frank. New York: Random House. 45 pp. $5.95. The Sky is Full of Song, by Lee Bennett Hopkins. New York: Harper & Row. 46 pp.

As a poet teaching in the public schools, I've come to believe that a simple creative writing program, incorporated into the yearly curriculum, can make the difference between a child who groans at the mention of the word ''poetry'' and one who finds the literary arts exciting and provocative. The formula, not at all surprising, consists of reading poems aloud for enjoyment and writing poetry together for a truly personal involvement. An introduction to poetry must focus on work that's accessible to a young listener, emphasizes the conjuring power of language, and reveals a direct link with the reader's own experience.

If you're searching for books to begin such a program, ''Knock at a Star'' is an ideal place to start. Mr. Kennedy has written books of poetry for both young and old audiences. He and his wife have created a writing-program and teaching anthology that explores the basic elements and styles of the poet's craft. The selection includes a broad spectrum of modern verse, with a strong emphasis on rhythmic invention, rhyme, and vivid imagery. Moving through each chapter, teacher, parent, or student can read and write their way into the pleasure of poetry. The styles presented are wonderfully varied, and described with a genuine sense of wonder. Karen Weinhaus's whimsical pencil drawings are a fine complement to the text. Children from Grade 3 and beyond will find this book a fine tool for poetic explorations.

It's never too early to begin reading poems to your young one. And so, for half a century, Josette Frank of the Bank Street College has been teaching, editing, and presenting poetry to children. ''Poems to Read to the Very Young'' brings together selections from her two well-known anthologies. The rhymed and metered poetry includes samplings of the classics: nursery songs, Kate Greenaway , and Stevenson's ''A Child's Garden.'' There are also offerings from writers like A.A. Milne and Jack Prelutsky to spice up the mixture. The large-format book is brightly colored with Eloise Wilkin's traditional illustrations.

For the 8- to 12-year-old audience, ''The Sky is Full of Song'' would make a fine addition to a poetry library. Lee Bennett Hopkins, well known as a writer and teacher, has written extensively on children's poetry. His new book is a lovely selection that steps through the four seasons accompanied by poets like Eve Merriam, Myra Cohn Livingston, and Gwendolyn Brooks. The poetry, both formal and free verse, is simple, spare, and quite enjoyable. With the addition of Dirk Zimmer's striking color linocuts, ''The Sky is Full of Song'' is an attractive packet of poetry for a young reader, pleasing to both the ear and eye.