Kimball led by six points with just under four minutes remaining, but Atwater-Cosmos-Grove City climbed past the Cubs thanks in part to a combined 40 points by Colton Minnick and Brody Larson.
Minnick tallied 23 points and Larson added 17 points. Kimball junior Jared Merchant scored a career-best 28 points and added eight rebounds for the Cubs (3-1). Senior guard Cameron Hunt finished with 16 points and five assists while junior Joey VonWahlde chipped in 13 points.
It was the first loss of the season for Kimball, which led 38-32 at the half.