The progress of a dancer from promise to fulfillment takes not only a lot of hard work behind the scenes, but also sufficient chance to test one's development onstage, in live performance. In two mixed repertory programs Friday and Saturday evenings at Kennedy Center, American Ballet Theatre provided such showcase opportunities for several of the company's younger members of conspicuous potential, with predictably varying but generally very encouraging results.

Two separate new casts had a crack at Anthony Tudor's oddball, quasi-dramatic "Tiller in the Fields," about nature taking its course in some prettily idealized rustic community, to woodsy, autumnal music by Antonin Dvorak. On Friday Lise Houlton used her sapling extensions and wren-like delicacy to much advantage in the role of the amorous intruder. But neither she, nor the more experienced, principal dancer Marianna Tcherkassky, dancing the same role the next evening with characteristic lyric sweetness, managed the mysterious elfin aura Gelsey Kirkland, the part's originator, gave us. And unfortunately, the more literal the interpretation, the sillier the ballet's premise seems.

Victor Barbee, partnering Houlton, was appealingly ingenuous and ardent; if he can smooth out some of his problems with physical coherence, he could be a formidale dancer. Dancing with Tcherkassky, David Loring displayed the lucidity, refinement and strength which mark him as a comer, but he seemed awakawardly at sea thus far with the dramatic content of "Tiller."

Barbee was effectively smoldering in "Miss Julie" Saturday, but Martine van Hamel looked out of her element with the erotic tempests of the title role. On Friday, Johan Renvall repeated his impressively charismatic debut as the jungle boy of Tudor's "Shadowplay"; he's a dancer with all the qualities for distinction except height.

Superlative dancing by Natalia Makarova and Patrick Bissell in the "Don Quixote" pas de deux, and Gelsey Kirkland and John Meehan in "Three Preludes," brought down the house deservedly on successive nights.

An account of Balachine's "Theme and Variations" featuring Eleanor D'Antuono and Kirk Peterson Saturday showed only that this matchless choreography can withstand even in different performance.