Ballet Tech KIDS DANCE, called "a New york City treasure!" in The New York Times, returns to The Joyce for 6 performances of Eliot Feld classics, June 6-9.    63 whiz-kids will take the stage in four feld favorites: A Stair Dance, dedicated to Gregory Hines; KYDZNY, a bubbly Balkin work effervescently danced by 39 remarkably poised and impeccably rehearsed kids, music by the Raya Brass Band; the effervescent trio Joggers; and Hello Fancy, Feld's first dance created for children in 1992, set to John Playford's The English Dancing Master.  The ensemble, ages 11-18, are all trained at Feld's tuition free Ballet Tech.