Two facts about St. Mary's are widely misreported, and both matter before a family applies. The first is the curriculum. Several directory sites describe the school as offering Advanced Placement. It does not. St. Mary's has been an authorized IB World School since 1979 and its high school is built entirely around the IB Diploma, with students choosing between the full Diploma and individual IB course certificates, all of them graduating with the school's own American-style diploma. A family that wants AP is looking at the wrong school here, and one that wants the IB has found a school that has run it for over four decades.
The second is timing. The school does not accept applications for Grade 12 at all, and it requires a boy to enroll by the beginning of Grade 11 and complete his final two full years there to finish the Diploma. That is a hard door rather than a preference, and it catches out families relocating with older teenagers. Everything else about the school follows from what it is: an all-boys Catholic school founded in 1954 by the Brothers of Christian Instruction, on a rebuilt nine-acre campus in Seta, in western Setagaya, with close to a thousand boys and around sixty nationalities.
Families ask about St. Mary's for two reasons: they want a boys' school, or they want a long-established IB program rather than a new one. Both are reasonable, and the school delivers on both. What we see families underweight is the English requirement. St. Mary's expects applicants to come from an English-medium school with two clean years of records, runs a compulsory screening test, and provides English support only up to Grade 8, with limited support in Grades 9 and 10 and none at all for a Grade 11 entrant. That is a stricter position than most schools in this guide take.
We teach families remotely across roughly eight countries, and we work with families in Japan, though our Japan experience to date is in Kansai rather than Tokyo. We are not a school, we have no affiliation with St. Mary's and no referral arrangement with any school in this guide. What we help with is the academic English and mathematics that screening test measures, and the writing and analysis a Diploma with six subjects and an extended essay demands. For a family from Taiwan or Hong Kong there is one gap to plan around: St. Mary's teaches no Chinese.
The orienting facts, each drawn from the school's own materials and the IB's own directory, checked in September 2026. Figures are the school's own, in Japanese yen, and are not converted.
St. Mary's is a non-profit school corporation governed by a board that includes members of the founding order, alumni, and former parents, though the leadership team has been lay-led since 2013. It is accredited by the Western Association of Schools and Colleges and the Council of International Schools, and has been an authorized IB World School since 1979, for the Diploma Programme only. It is not an Article 1 school under Japanese law, a point the school states plainly itself. And it publishes its fees in full, in yen, which is why this guide can carry them.
St. Mary's publishes a full fee schedule, billed annually and prorated by quarter if a family withdraws. The tables below are the school's own figures for the 2026 to 2027 year, in yen, and this guide does not convert them.
A new family pays ¥1,450,000 before tuition: ¥50,000 to apply, a registration fee of ¥400,000, and a development fund contribution of ¥1,000,000, all non-refundable, and the school states plainly that paying the application fee guarantees nothing. An annual building maintenance fee of ¥200,000 applies every year. Returning families pay a re-enrollment seat deposit of ¥300,000, which is credited against tuition rather than refunded. Devices are charged separately in Grades 3 and 6, and IB examinations cost ¥20,000 a subject in the final years.
Billed annually. Excludes the ¥200,000 annual building maintenance fee.
| Grade band | Per year | With building fee |
|---|---|---|
| Elementary | ¥2,860,000 | ¥3,060,000 |
| Middle school | ¥2,970,000 | ¥3,170,000 |
| High school | ¥3,050,000 | ¥3,250,000 |
Source: the school's own tuition and fees page, 2026 to 2027 schedule. Checked September 2026.
| Item | Amount | Applies to |
|---|---|---|
| Application fee | ¥50,000 | Per application, non-refundable. Does not guarantee a place |
| Registration fee | ¥400,000 | New students, one time, non-refundable |
| Development fund | ¥1,000,000 | New students, one time, non-refundable |
| Building maintenance | ¥200,000 | Annual, non-refundable |
| Re-enrollment seat deposit | ¥300,000 | Returning students. Credited against tuition, not refunded |
| School bus | ¥310,000 one way, ¥420,000 both ways | Per year, optional |
| IB examinations | ¥20,000 per subject | Billed in December of the examination year |
| Devices, graduation | Charged separately | An iPad in Grade 3, a laptop in Grade 6, and ¥30,000 at graduation |
For a new Grade 9 boy in 2026 to 2027, tuition of ¥3,050,000 plus the building maintenance fee of ¥200,000 and the one-time fees of ¥1,450,000 comes to ¥4,700,000 before the bus, devices, and examination entries. Adding a return bus place brings it to ¥5,120,000. Later years fall back to tuition plus the ¥200,000 building fee. These totals are Harland's arithmetic on the school's own figures, labelled as such.
| Grades served | Readiness Program at age five to Grade 12, boys throughout. Age cut-off 1 September |
|---|---|
| Enrollment | Close to 1,000 boys. The homepage says around 60 nationalities and the about page nearly 50. No exact count is published |
| Curriculum | American standards-based through middle school, then IB preparatory in Grades 9 and 10 and the IB Diploma in 11 and 12. No Advanced Placement |
| IB authorisation | An IB World School since 1 September 1979, for the Diploma Programme only. No Primary Years or Middle Years Programme |
| Graduation | The St. Mary's high school diploma, minimum 27 credits, with the IB Diploma alongside it for candidates who earn it |
| Accreditation | WASC since 1972 and the Council of International Schools since 2001. Not an Article 1 school under Japanese law |
| Languages | Japanese from Grade 2, with native and second-language tracks carried to IB level. French and Spanish offered. No Chinese |
| English support | Available to Grade 8, limited in Grades 9 and 10, and unavailable to Grade 11 entrants because of the Diploma |
| Admissions | Rolling, subject to seats, except no Grade 12 entry and no Readiness Program entry after January. A compulsory screening test applies |
| Eligibility | Applicants should come from an English-medium school. Priority for Catholic applicants, brothers, sons of alumni, and children of staff |
Where the school's own pages differ, as on the number of nationalities, both figures are shown rather than merged. All figures in yen, checked September 2026.
St. Mary's was founded by a Catholic teaching order and still carries its character, though the Brothers no longer run it day to day.
The school opened in September 1954, founded by the Brothers of Christian Instruction, a French teaching order established in 1819, to provide a Catholic education for boys in Tokyo. It began near Sengaku-ji in Minato and moved to its present campus in Seta, western Setagaya, in 1971, where an eleven-year rebuilding project finished around 2009 and produced the campus a family sees today. The school formed its own school corporation in 2012, and since 2013 its leadership team has been lay rather than religious, carrying on what it calls the spirit of the Brothers rather than their direct governance.
Its guiding statements set out beliefs in personal development, academic excellence, co-curricular enrichment, and what it names explicitly as an all-boy environment, alongside love and respect for the dignity of humankind created in God's image. The school expects its families to support that mission, and it welcomes boys of all faiths while giving Catholic applicants priority in admission. A Brothers' residence and a chapel remain on the campus. The school runs joint plays, musicals, Model United Nations, and a combined swim team with its sister school Seisen International School, the girls' Catholic school nearby, which is also where many families with daughters look. Dr. Andrew Davies became Head of School in August 2025, though the school's own leadership page presents names as images rather than text, so a family should confirm current appointments directly.
The lower school is American and standards-based. The high school is built around the IB Diploma, which the school has run since 1979, and there is no Advanced Placement anywhere in it.
Elementary, from the Readiness Program at age five to Grade 5, teaches to American standards, Common Core in English and mathematics, the Next Generation standards in science, and a recognized international framework in social studies, alongside three religion strands from which a family chooses: Catholic, Christian, or character development. Japanese begins in Grade 2, explicitly to prepare boys for Japanese at IB level later. Middle school continues the standards-based model, and Grades 9 and 10 are described as IB preparatory rather than as a separate qualification. The school runs neither the Primary Years nor the Middle Years Programme, so the IB arrives only at the end.
In Grades 11 and 12 every boy takes IB courses, and the choice is between the full Diploma, with three higher-level and three standard-level subjects plus theory of knowledge, an extended essay, and the service requirement, and the IB Course Program, which allows individual certificates with fewer requirements. Every graduate earns the school's own diploma of at least twenty-seven credits, and Diploma candidates earn the IB Diploma alongside it. Japanese is carried to the highest level, offered as a first language and as a second, so a bilingual boy continues developing real literacy. There is no Chinese at all, which matters for a family arriving from Taiwan or Hong Kong. Among the schools in this guide only The British School in Tokyo teaches Mandarin.
St. Mary's publishes results in a school profile, and the most recent version this guide could read carries figures from 2022 and 2023 rather than the current year.
In that profile the school reports an average IB Diploma score of 37 for 2022, against a worldwide mean of 32 that year, with 48 candidates and 48 diplomas awarded, and comparable numbers in the three preceding years. It also states that more than 85 percent of its Grade 11 and 12 students are full Diploma candidates, which is a high proportion and tells a family that the Diploma is the school's mainstream route rather than a track for a strong minority. For the class of 2023 the middle half of SAT scores ran from 1200 to 1420, with a mean of 1320.
Those figures are dated, and the school's current profile sits in a document this guide could not read, so a family should ask admissions for the latest edition rather than treat the numbers above as this year's. And the destination lists the school publishes, which span Dartmouth, Carnegie Mellon, Johns Hopkins, Chicago, Pennsylvania, Imperial, Oxford, Cambridge, and the University of Tokyo across several graduating classes, are lists of where boys have gone rather than a count of any single cohort. The school does not rank its students, and it weights IB courses in its grade point average.
Applications are accepted through the year subject to seats, with two exceptions that matter. The Readiness Program closes to applications once the second semester begins in January, and Grade 12 is closed entirely, with the school stating that a boy must enroll by the start of Grade 11 and complete his final two full years there to finish the Diploma. Every applicant sits a compulsory screening, an oral interview with an English examination, a mathematics screening, and a writing sample, and the youngest applicants attend a group observation with a family interview instead. The school does not re-test or reconsider within the same school year, so a single attempt is what a family gets.
Where a grade is full, boys are waitlisted and ranked by screening result rather than by application date, so applying early does not by itself secure a place, though the school gives priority consideration to Catholic applicants, brothers of current students, sons of alumni, and children of staff. And the English support runs out as a boy gets older: it is available to Grade 8, limited in Grades 9 and 10, and unavailable to a Grade 11 entrant because of the Diploma. A family with a son who is still building English should be looking at the lower grades or at another school.
Harland is not a school and does not replace St. Mary's. We are a 1-on-1 tutoring academy, and we work with families in Japan and across roughly eight countries remotely, in the three places this school's requirements create real work for a family: the screening, the years before the Diploma, and the Diploma itself.
The IB, and only the IB. The school has been an authorized IB World School since 1979 and runs the Diploma Programme in Grades 11 and 12, with students choosing between the full Diploma and individual IB course certificates. It offers no Advanced Placement, despite what several directory sites claim. Every graduate receives the school's own American-style high school diploma, and Diploma candidates earn the IB Diploma alongside it.
No. The school states plainly that it does not accept applications for Grade 12, and that a student must enroll by the beginning of Grade 11 and complete his final two full years at the school to finish the IB Diploma. A family arriving in Tokyo with a rising Grade 12 son needs a different school, and one arriving in Grade 10 or 11 should apply promptly.
For 2026 to 2027 the school publishes annual tuition of ¥2,860,000 for elementary, ¥2,970,000 for middle school, and ¥3,050,000 for high school. A new family also pays ¥50,000 to apply, a registration fee of ¥400,000, and a development fund contribution of ¥1,000,000, none refundable, plus an annual building maintenance fee of ¥200,000. So a first year in the high school comes to about ¥4,700,000 before the bus, devices, and examination fees.
No, the school welcomes boys of all faiths, and religion classes in the elementary years include a character development strand alongside the Catholic and Christian ones. Being Catholic does affect admission, though: the school lists Catholic students among the groups given priority consideration, alongside brothers of current students, sons of alumni, and children of staff. Families are expected to support the school's mission rather than to share its faith.
Yes, with conditions the school sets out unusually clearly. It states that St. Mary's does not hold Article 1 status, that Japanese parents are legally required to send children to Article 1 schools for the nine compulsory years, and that they must give full consideration to that before applying. It then admits qualified Japanese citizens whose recent education has been in English, or who have an English-speaking expatriate parent.
Our Student Coordinator speaks with relocating families regularly, often before a posting is confirmed, and can help you think through the entry deadlines, what the screening involves, and whether the timing works for an older boy. We work with families remotely. We start by listening.