Where is naperville school district 203 located? Naperville Community Unit School District 203 is a school district headquartered in Naperville, Illinois, United States.What is the best school district in naperville il? Naperville Community Unit School District No. 203 is a top rated, public school district located in Naperville, IL.What is district 203 known for? District 203, established in 1972 through the merger of elementary and high school districts, serves central Naperville (as well as portions of neighboring Lisle and Bolingbrook). All but two of the district's buildings are within the limits of the city of Naperville. Kennedy Junior High School is in Lisle.