It's too bad that Ellen Conford seems to be losing her light touch. In this latest growing-up go-round you almost have no choice but to take her whiney, painin-the-neck heroine as seriously as she does herself. Transplanted to a New York City suburb, the latest rung in Daddy's climb up the corporate ladder, eleven-year-old Wallis faces the awesome task of fitting in at the Briar Lane School. Ready to do almost ""anything for a friend,"" Wallis not only agrees to help Stuffy, the neighborhood bad boy, pen phony love letters from their male teacher to the class nerd, but she also lets this junior hustler plan a rather dubious seance at her house. (It seems the former owner had his brains blown out by a jealous wife and Stuffy, who is secretly charging admission to the show, plans to raise the spirit of the departed Don Juan.) At least Conford is no moralist, and despite her heroine's less-than-noble bid for popularity, she does allow Wallis her hour with the in crowd--that is, until Daddy breaks the news of their imminent move to the West Coast. Then too, realistically, the class misfit remains to the end a rather boring leech. Don't go looking for sharp insights about the tricky business of being or getting a friend, but the close observations of pre-teen pecking order and grade-school protocol will probably elicit painful nods of recognition.