The premise is blatantly familiar--boy athlete becomes a very reluctant ballet performer--but, with gentle humor and a lower-middle-class British accent, Ute (See You Thursday) gives the predictable conflicts a fresh injection of easygoing charm. Jamie Carr, 16, is an unpromising student at Tenterden Road Comprehensive (some amusing grappling with math), a would-be baseball star, and the older brother of ballet-mad Kim--whom he has to fetch (""all beaming and porky"") from her Friday-night class every week. So, when an upcoming charity recital loses its only ablebodied male, charismatic Miss Tucker grabs hold of likely-looking Jamie, testing his rhythmic sense in an impromptu pas de deux. (""It ought by rights to have been the most embarrassing thing that ever happened to him--disco dancing to the wrong sort of music with a daft old bat as old as his grandmother. Oddly enough, it wasn't."") Jamie protests and tries to sneak away, of course. Miss Tucker--and posh top-ballerina Anita--persist. Soon, then, Jamie is learning to partner the lovely (if single-minded) Anita; he's even persuaded to undertake a Russian-style solo of his own. And, half-inspired by a TV viewing (with Anita) of Nureyev in Romeo and Juliet, Jamie starts actually enjoying this new challenge--despite the mortification of white tights, despite his father's cheerfully cruel jibes, despite conflicts with baseball, twinges of sexual insecurity. . . and mid-performance taunts from local louts. (Jamie keeps dancing--and finally seems to win Anita's admiration as a person, not just a partner.) Textured with class-conflicts, credible supporting players, and tart dialogue: an appealing English re-run of a standard scenario.