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St. Mary's International School — a Boys-Only School Open to All Faiths

Tokyo, Japan

A Catholic-founded, boys-only school across every grade — reportedly open to boys of any faith, not Catholics exclusively.

Researched by William Prep from published sources. Not yet verified by the school. — Last reviewed by William Prep: 2026-09-24

St. Mary's was founded in 1954 by the Brothers of Christian Instruction as a boys' school, moving to its current Setagaya-ku campus in 1971. Every grade is boys-only, and the school reportedly offers the IB Diploma at the high-school level.

At a Glance

Coeducation	Boys-only, all grades (not independently confirmed)as of: 2026-09-24
Faith Policy	Catholic-founded, open to all faiths (not independently confirmed)as of: 2026-09-24
Curriculum	IB Diploma (high school) (not independently confirmed)as of: 2026-09-24
Est. First-Year Cost (Elementary)	≈¥4.51M2026-27 · as of: 2026-09-24

Catholic-Founded, but Reportedly Open to All Faiths

The school's founding mission is Catholic education, but it reportedly now welcomes boys of any faith, not Catholics exclusively. The assumption that "Catholic-founded" means "Catholics only" doesn't hold here.

William Prep’s Analysis

How much daily worship or religious instruction is actually built into the curriculum matters differently to different families, so a family considering St. Mary's regardless of faith background should ask the school directly what religious education actually looks like day to day, rather than assume from the "Catholic-founded" label alone.

Fees: A Real First-Year Total of About ¥4.51M (Elementary)

St. Mary's own 2026-27 fee schedule lists three non-refundable one-time charges for new students: a ¥50,000 application fee, a ¥400,000 registration fee, and a ¥1,000,000 development fund. On top of that, an annual ¥200,000 building maintenance fee applies alongside grade-banded tuition (¥2,860,000 for Elementary). Added together, a genuine first-year total comes to roughly ¥4,510,000.

University Entrance Eligibility in Japan

School-accreditation route	Yes (not independently confirmed)
Student-qualification route (IB, etc.)	Yes

The WASC/CIS accreditation is based on third-party reporting, not confirmed against either registry directly this session. Independent of that, a student completing the full IB Diploma qualifies via the individual-credential route regardless.

Fees & Estimated First-Year Cost

academic year: 2026-27

Application Fee	¥50,000
Registration (new students)	¥400,000
Development Fund (new students)	¥1,000,000
Building Maintenance Fee	¥200,000
Tuition (Elementary)Elementary	¥2,860,000
Tuition (Middle School)Middle	¥2,970,000
Tuition (High School)High	¥3,050,000
Estimated First-Year Total	¥4,510,000

Includes: application, registration, capital, facilities, tuition — Excludes: Excludes IB exam fees (¥20,000/subject), the Grade 12 graduation fee, and iPad/MacBook costs. This uses Elementary tuition as the base.

What Makes This School Distinctive

An interfaith-open policy inside a Catholic-founded boys' school

Catholic-founded, but reportedly open to boys of any faith

Multiple search-aggregated sources report the all-faiths policy consistently.

Families who ruled out Catholic-founded schools on religious grounds may want to reconsider, given this reported policy.

Admissions

Cycle

未確認 not publicly confirmed

What Japanese Families Should Know

Who Might Find This School a Good Fit

Might suit — Families specifically seeking a boys-only environment

Might not suit — Families wanting coeducation, or with a daughter to enroll

William Prep’s Analysis

Researching St. Mary's surfaced a useful correction to a common assumption: "Catholic-founded" doesn't automatically mean "Catholics only" here. It's worth checking a school's actual admissions policy before ruling it out on religious grounds.

Questions to Ask the School

1.How much religious instruction or worship is actually part of the day-to-day curriculum?
Why this matters: Not confirmed this session.
2.What is the current status of the WASC and CIS accreditations?
Why this matters: Not confirmed against either registry directly this session.

Sources & Verification

Tuition & Fees — St. Mary's International Schoolprimary source · as of: 2026-09-24Fetched directly. 2026-27: application ¥50,000, registration ¥400,000, development fund ¥1,000,000 (one-time, new students), building maintenance ¥200,000/yr, tuition by school level. Re-enrollment seat deposit ¥300,000 for returning students (credited toward tuition).
Search synthesis on SMIS history and accreditation — Multiple (incl. Wikipedia)third-party source · as of: 2026-09-24Founded 1954 by the Brothers of Christian Instruction as a Catholic school for boys; welcomes boys of all faiths (not Catholics only). Moved from Takanawa to its current Setagaya campus in 1971. Boys-only. WASC and CIS accredited. Note: distinct institution from Marist Brothers International School in Kobe, which some sources conflate with it. Not independently confirmed against smis.ac.jp's own history/accreditation pages this session.
大学入学資格について — 文部科学省 (MEXT)official source · as of: 2026-09-23Sets out the routes to 大学入学資格: MEXT-designated schools; graduates of 12-year programmes at institutions accredited by WASC, CIS, ACSI, NEASC, Cognia or COBIS; holders of the IB Diploma, Abitur, Baccalauréat, GCE A-Level, International A-Level or European Baccalaureate; 高等学校卒業程度認定試験 (age-18 gated); and individual university review at 18+.

Last reviewed by William Prep: 2026-09-24

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