VanderPol was 10 of 15 from the field and had nine rebounds and three blocks to lead the Lady Spartans despite being in foul trouble for much of the game.
Grundy Center established control from the outset, leading 18-16 at the end of the first quarter and went into halftime with a 33-24 lead. Mid-Prairie would come no closer than five points in the second half as the Lady Spartans advanced to the 2A semifinals with the 61-49 victory.
VanderPol's 24 points overshadowed a balanced Grundy Center attack that saw four players score eight or more points. Chelsie Luhring, Katie Schuller and Danielle Zimmerman all had eight points for the Lady Spartans. Zimmerman also added 11 rebounds off the bench.
Mid-Prairie was led by Jessie Kleinschmidt's 12 points and six steals.
Grundy Center will play either Sioux Center or Battle Creek-Ida Grove at 2:30 p.m. Thursday.
Grundy Center (23-3) 18 15 11 17 -- 61
Mid-Prairie (21-6) 16 8 11 14 -- 49