CASTLE HILLS Castle Hills is a 2,800-acre master-planned community that opened to residents in 1998. Started development: 1997 Square footage: 1,240-7,142 Home values: $292,806-$1,849,900 Median price per square foot: $149.88 Median days on the market: 60 HOA dues (estimated): $740 annually Amenities: 25 parks, five community pools, hike/bike trails, 12-acre park with lake Schools: Hebron High School, Killian Middle School, Castle Hills Elementary School, Independence Elementary School, The Colony High School, Griffin Middle School, Morningside Elementary School, Polser Elementary School, Creek Valley Middle School