It's 17-year-old Kim Kenyon's last year to win recognition as a junior rider and make the U.S. Equestrian Team--and her only assets are a promising horse, Fox-fire, and the determination her mother calls obstinacy. A bystander might be less complimentary still, for Kim is bitterly resentful toward her far-from-rich parents for balking at the costs of competitive riding (""One hundred and fifty dollars a month [for Foxy's winter board] seemed a lot to them. Plus lessons. . . . And classes at shows. . . and the one hundred and thirty dollar riding jacket and custom-made boots""); where they'd get that kind of money, even if they were ultra-enthusiastic (and, say, let her skip school on Mondays after a Sunday show), is something that never seems to enter her mind. She also bridles at a judge's unfair (?) judgment of her performance and dismisses a prospective riding teacher because he's ""a Displaced Person from somewhere in Eastern Europe"" with a thick accent. An ungracious, even nasty sort. So she rates few cheers when, through a combination of luck, ""connections,"" and stringent training, her riding and her chances improve; and, correspondingly, garners little sympathy when she learns that, as she's been warned, the ability to provide a string of good horses (i.e., money), not the ability to ride (""There must be a thousand good kids like you. . .""), wins a berth on the team. A poor show all 'round.