Peter Kyo Won Koo, a 15-year-old from Chandler who plays golf for Hamilton High School, summed it up in one word when told he had a share of the lead at the midpoint of the Arizona Stroke Play Championship.

“Cool,’’ said Koo, who carded a one-under-par 69 at the TPC Scottsdale’s Champions Course on Friday, a number that got him to one-under 139 along with Tucson teen-ager Alex McMahon, Scottsdale’s Andrew Medley and Justin Harding, an Arizona State student from Fredericksburg, Va.

“My coach said that Hamilton guys have done well in this tournament in the past. Truthfully, I didn’t even know about (the tournament) until a week ago. But now that I’m close, I’m going to try (to win it).’’

Koo, who recently won the Junior Golf Association of Arizona’s Thunderbird Invitational, McMahon (65), Medley (67) and Harding (69) are one shot better than Camron Howell (70) of Apache Junction. Among the notables, first-round leader Michael Wog (75) of Scottsdale fell into a tie for eighth place at 4-over.

And like Koo said, he’s got a little history going for him. The last four Stroke Play Championships have been won by Chan Kim (2008, 2010) and Andrew Yun (2007, 2009), both former Hamilton High alums.

The 36-hole cut came at 151 with 64 players moving on to the weekend. Play starts Saturday and Sunday at 7:30 a.m.

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