Rosalynn Carter has found the formula, sought by most mothers of 9-years-olds children, for parting her daughter Amy from her favorite gear of jeans and jumpsuits.

By letting Amy have a say in the selection, and picking clothes as tailored, easy fitting and almost as comfortable as jeans, Mrs. Carter has put together a small wardrobe for Amy to choose from for the week long Inaugural festivities and well after.

The clothes are by Ceil Ainsworth, New York children's wear designer, whose dresses Amy and her mother have selected before from the Tot Shop in Americus, Ga. In fact, one of the coats ordered from Ainsworth was chosen to go over a dress Amy has worn in the past.

Among the choices: a clear, sk-blue, long velvet dress with white eyelet collar and cuffs with matching hooded cape, a navy velveteen jumper with white blouse and navy coat trimmed in velvet with a matching hat, and a green coat with West Point-style cape and matching hat to wear over the green jumper she already owns.

Amy was quizzical about the ear flaps on the hats, but Ainsworth assured her they might be necessary in Washington and explained the heavy coat the same way.

Ainsworth went into the the business of designing clothes for little girls nine years ago when she couldn't find the things she wanted her 2-year-old daughter Susan to wear. That meant little pinafore dresses in particular. As her own child got older she added dresses and sportswear for older girls.

The clothes chosen for Amy are from the holiday season just past at Ceil Ainsworth's. All have deep hems, which should hold Amy for two years, Ainsworth believes.

Amy Carter's style, which is not very different for the Caroline Kennedy-Best & Co. chic of the early 1960s, is likely to have a strong influence on the childrens wear industry in bringing in tasteful and tailored clothes as an alternative to rugged jeans, turtlenecks and T-shirts.

And can't you hear mothers saying to their children in dressing rooms across the country. "But it Amy can wear a dress, why can't you?"