Now after a search, to the right of the map you will see an option to show School Boundary Zones, also know as School Attendance Zones.
Currently we only have Fairfax, Arlington and Washington DC. If you all like it, maybe we can add more.
Disclaimer: Don't buy a home solely based on this data. We also have a "Verify School" link. But ultimately if a school is crucial to your purchase, you need to call the district to verify that everything is up to date and nothing is changing.
Also let me know if you think anything is wrong.
Note this data IGNORES the agent school input field and is based solely on the county maps.