Chris DeForest of Cottekill, N.Y., shot a 3-over 74 at Westfield Group Country Club to finish at 10-under 274, winning the boys' title by six shots over Mark Johnson of Tulsa, Okla.
The 12-year-old Thompson, from Coral Springs, Fla., who missed the cut in the Open at Pine Needles last month, began the day tied with Kim. But after falling behind early, Thompson birdied four of five holes beginning at the par-4 12th to pull ahead.
She finished with a 2-under 69 and a 1-under 283 total, becoming the youngest champion in the 32-year history of the Junior PGA. Kim, a 15-year-old player from Pahoa, Hawaii, shot a 1-under 70 to finish a shot back. Cassandra Blaney, a 17-year-old golfer from Davenport, Fla., closed with a 71 to finish three strokes back in third.
The 17-year-old DeForest, who will play golf at the University of Illinois, fell three shots off the 72-hole record of 271, set by Pat Perez in 1993.
Johnson, who will play for Oklahoma State this fall, also closed with a 74 to finish at 4-under 280. Luke Guthrie of Quincy, Ill., was another shot back in third after a final-round 71.
The Junior PGA Championship is one of the premier junior championships of the summer. It features 156 boys and girls who are 18 and under and haven't started college. Past champions include David Toms, Trevor Immelman, Billy Mayfair, Cristie Kerr and Grace Park.
It was one of the few junior events not won by Tiger Woods, who finished second to Chris Couch in 1990.
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