In the U.S., moving from the city to the suburbs is probably the best thing you can do to ensure decent public schooling. For instance, a recent list of top ranked public high schools from US News and World Report:
Academic Magnet High School, South Carolina
Maine School of Science and Mathematics
BASIS Scottsdale, Arizona
Thomas Jefferson High School for Science and Technology, Virginia
Central Magnet School, Tennessee
Gwinnett School of Mathematics, Science and Technology, Georgia
Haas Hall Academy, Arkansas
International Academy of Macomb, Michigan
Payton College Preparatory High School, Illinois
Signature School, Indiana