Very cool nationwide online map of district boundaries just released: https://nces.ed.gov/ccd/schoolmap/ Not yet able to download the files that would allow you to import into your SIS, but this looks promising.
The U.S. Department of Education tool, School & District Navigator, was developed to provide a geographic presentation of the Common Core of Data's (CCD) public school and public school district datasets.
The CCD is a program of the U.S. Department of Educations National Center for Education Statistics that annually collects fiscal and non-fiscal data about all public schools, public school districts and state education agencies in the United States.
The data are supplied by state education agency officials and include information that describes schools and school districts, including name, address, and phone number; descriptive information about students and staff, including demographics; and fiscal data, including revenues and current expenditures.
For more information about the data, please visit the CCD website.