Sports
Junior High and High School sports offered include: tennis, volleyball, cross country, swimming, basketball, soccer, badminton, and track and field. Ping-pong is also offered, but only as an optional weekly activity. Students participating on Varsity or Junior Varsity teams are eligible for a Varsity or Junior Varsity Letter.
Seisen competes with other international schools and U.S. Military schools as well as Japanese schools. Seisen participates in the Kanto Plains league for tennis, volleyball, soccer, basketball, cross country, and track and field. The teams are supported by the Girls Athletic Association (GAA).