Seisen International School
🇯🇵 Tokyo · Founded 1962 · IB · Ages 2–18
A well-established Catholic, girls'-school (co-ed kindergarten) IB continuum school in Setagaya, with strong dual CIS + NEASC accreditation and a 60+ year history.
Curricula
IB
Age range
2–18
Languages of instruction
English
Annual fees
SGD JPY 2,650,000–2,850,000
Enrollment
695
Boarding
No (day school)
IB authorised
PYP, MYP, DP
Accreditations
CIS, NEASC, JCIS
Tier Profile
We only tier dimensions backed by a public inspection verdict or verifiable accreditation. Other dimensions show a data flag — never a guessed score.
BrightKey's Assessment
Seisen International School is a Catholic international school in Yoga, Setagaya-ku, Tokyo, founded in 1962 and sponsored by the Handmaids of the Sacred Heart of Jesus. It describes itself as 'first and foremost a Catholic international school' and marked its 60th anniversary in 2022.
Its defining identity is single-sex: education is provided to girls only for Grades 1–12, while the Kindergarten is co-educational. Seisen was the first girls' school in Japan to offer the IB Diploma Programme (since 1986).
Academically, Seisen is a full IB Continuum World School — PYP (authorized 2007), MYP (added 2019) and DP (since 1986). Instruction is in English with EAL support; additional languages include French, Japanese and Spanish.
The school is CIS- and NEASC-accredited and a JCIS member. Reported enrollment is 695 students across 42 nationalities with small classes. It reports 98% of graduates proceeding to higher education — a school-reported, unverified figure.
Why These Ratings?
Inspection & AccreditationA — Excellent
Strong dual CIS + NEASC accreditation plus JCIS membership. Japan has no public inspectorate, so the tier reflects accreditation depth — A.
Strengths & Trade-offs
Strengths
- Full IB continuum (PYP + MYP + DP) under one roof — strong vertical academic coherence
- Strong dual international accreditation: CIS + NEASC, plus JCIS membership
- Long-established (since 1962) with a clear, distinctive Catholic, girls'-school identity
- Documented EAL support plus dedicated learning-support specialists
- Small class sizes (average ~20) and a low reported student-faculty ratio
- Genuinely international community (42 nationalities, balanced local/international mix)
Trade-offs
- IB Diploma results / average scores are not published — academic outcomes cannot be independently verified
- Tuition is not published on the official site; fee data is third-party (school-reported) only
- Single-sex from Grade 1 onward excludes boys beyond kindergarten
- Catholic sponsorship may not suit families seeking a fully secular environment
- No boarding — day-school only
Is It Right For You?
Best For
- ✓Families seeking a single-sex environment for girls within a rigorous IB pathway
- ✓Families who value a faith-rooted (Catholic) ethos with cultural/religious inclusivity
- ✓Younger families wanting a co-ed start in kindergarten that transitions to girls-only
- ✓Students needing EAL support entering an English-medium IB programme
Not Ideal For
- ✕Families with boys beyond kindergarten age (girls-only Grades 1–12)
- ✕Families wanting co-education throughout
- ✕Families seeking a strictly secular school
- ✕Families needing boarding or based outside the Tokyo commute zone
Curriculum
IB Continuum World School: PYP (authorized 2007), MYP (added 2019), DP (since 1986). Instruction in English with EAL support; additional languages French, Japanese, Spanish. IB Diploma outcomes are not published.
Fees
The official website does not publish tuition. International Schools Database reports approximately JPY 2,650,000–2,850,000 for 2026/2027 — school-reported via a third party and unverified against the official source. Confirm directly with admissions.
Admissions
Kindergarten is co-educational; Grades 1–12 are girls-only. Specific admissions pages were not publicly retrievable — confirm current criteria directly with the school.
Campus Life
Located at 1-12-15 Yoga, Setagaya-ku. Operates within a Catholic ethos ('Love in Action'); shares school-bus services with neighbouring St. Mary's International School (the boys' counterpart). Small classes, diverse student body.
University Placement
School-reported · not independently verified
School-reported, unverified: Seisen reports that 98% of graduates proceed to a higher educational institution. No specific university-destination lists or IB score averages are published.
Sources
Every verifiable fact carries a public source — verify it yourself.
- Seisen International School (official) · 2026-06
- Seisen — About (official) · 2026-06
- International Schools Database — Seisen Tokyo · 2026-06
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