K. International School Tokyo vs Seisen International School
🇯🇵 Tokyo · Side-by-side comparison on verifiable public data.
Neither K. International School Tokyo nor Seisen International School sits in a market with a public inspectorate, so both are assessed on verifiable accreditation, curriculum authorisation, and published data rather than an official quality rating. Both are day schools with fees in the same market band — see the table below for the figures, and verify against each school's own published fees.
Key Facts
| K. International School Tokyo | Seisen International School | |
|---|---|---|
| Curriculum | IB / British | IB |
| Ages | 3–18 | 2–18 |
| Languages of instruction | English | English |
| Annual fees | JPY 2,850,000–3,020,000 | JPY 2,650,000–2,850,000 |
| Enrollment | 660 | 695 |
| Boarding | Day only | Day only |
| Accreditations | CIS, Edexcel | CIS, NEASC, JCIS |
Strengths
- ✓Outstanding, transparently published IB DP results (42.0/45 in 2025; five-year track record above 41)
- ✓Full CIS accreditation on a 5-year evaluation cycle — strong external quality assurance
- ✓Single-campus K1–G12 continuity (ages 3–18) — no transition between schools
- ✓Central, highly accessible Tokyo location (Shirakawa, Koto-ku); new 2024 main building
- ✓Established history (since 1997) with deep IB roots (IB World School since 2002)
- ✓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
Trade-offs
- !No EAL/language support for Grade 8 and above — students needing English help are explicitly not accepted
- !The IB continuum is incomplete in practice: MYP is no longer offered, and middle years run on Edexcel iLowerSecondary/IGCSE
- !High fees (~¥2.85M–3.02M annual tuition plus ¥700K capital and other one-time fees)
- !Third-party review sentiment is weak (small, unverified sample)
- !Enrollment/nationality figures differ between official site (~700/50+) and aggregators (660/45)
- !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
Best Fit For
- • Families seeking a top-tier, results-driven IB Diploma outcome
- • Children entering in the early years (K1–early primary) who can grow up in the system
- • English-fluent international and bilingual families based in central/east Tokyo
- • 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
University Placement
School-reported · not independently verified
School-reported: KIST publishes detailed IB DP results (42.0/45 average, 100% pass rate, 25% scoring 45 in 2025). A university-acceptance page exists but specific destination figures were not captured; treat placement claims as school-reported, unverified.
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.
More Comparisons
Frequently Asked Questions
Should I choose K. International School Tokyo or Seisen International School?
K. International School Tokyo is best for: Families seeking a top-tier, results-driven IB Diploma outcome. Seisen International School is best for: Families seeking a single-sex environment for girls within a rigorous IB pathway. The right choice depends on target curriculum, budget, and family priorities — the two are not linearly comparable.
How do fees compare between K. International School Tokyo and Seisen International School?
K. International School Tokyo: JPY 2,850,000–3,020,000. Seisen International School: JPY 2,650,000–2,850,000. Verify against each school's own published fees; some figures are sourced from third-party aggregators.
What curricula do K. International School Tokyo and Seisen International School offer?
K. International School Tokyo: IB, British. Seisen International School: IB.
Do K. International School Tokyo or Seisen International School offer boarding?
K. International School Tokyo: day school only. Seisen International School: day school only.
This comparison is BrightKey's independent assessment using verifiable public data only. University-placement figures are school-reported and not independently verified. BrightKey takes no payments from schools. Our method →