Anything south and east of Saylorville Lake is Ankeny enrollment. Any home within Polk City is North Polk Schools. When the new homes are built east of the Polk City cemetery, those will be Ankeny CSD. Rural homes SE of the lake and wildlife refuge may have a Polk City address but are within Ankeny boundaries.
Conversely, anything north of 54th Street on the NE edge of Ankeny is North Polk enrollment. Basically, anything that falls to the north of halfway between Exit 94 and Exit 96. NP receives far more from that section of town than Ankeny receives from Polk City.
Also, NP was 2A less than 10 years ago. Just 7 years ago, they were #99 with 328 for the BEDS count and are up to #65 at 487, so they are rising rapidly. The growth is still bubbling up through the elementary grades. Gilbert was on a very similar trajectory a decade ago