International School of London vs Marymount International School London
🇬🇧 London · Side-by-side comparison on verifiable public data.
Both carry a public inspection verdict: International School of London is Ofsted "Good" and Marymount International School London is Independent Schools Inspectorate (ISI) "Excellent" — a rare pairing where an official quality rating can be compared head-to-head. Both run the same curriculum (IB), so the differences come down to pathway detail, campus culture, and specific language/boarding arrangements rather than the curriculum framework itself. One practical difference: Marymount International School London offers boarding while the other is day-only — decisive for families who need a residential option. Verify current fees against each school's own figures (see the table below).
Key Facts
| International School of London | Marymount International School London | |
|---|---|---|
| Curriculum | IB | IB |
| Ages | 3-18 | 11-18 |
| Languages of instruction | English | English |
| Annual fees | £24,630–£39,640/year (2026/2027, ages 3–17; figures incl. VAT where applicable) | Day GBP 39,540/yr; full boarding GBP 66,990/yr (2026-27, incl. VAT) |
| Enrollment | — | 250 |
| Boarding | Day only | Yes |
| Inspection rating | Ofsted: Good | Independent Schools Inspectorate (ISI): Excellent |
| Accreditations | Council of International Schools (CIS), International Baccalaureate Organization (IBO) | Council of International Schools (CIS), Middle States Association of Colleges and Schools, International Baccalaureate Organisation (IBO) |
Strengths
- ✓Exceptional mother-tongue programme — 24 home languages taught as part of the curriculum, a genuine sector outlier
- ✓Strong bilingual outcomes — about half of leavers earn the bilingual IB Diploma, well above the IB world average
- ✓Full IB continuum (PYP, MYP, DP) under one provider, giving age-3-to-18 curricular coherence
- ✓Long pedigree and accreditation — founded 1972, CIS-accredited, authorised IB World School (code 000057)
- ✓Genuinely international and non-selective — 54 student nationalities across the IB programmes, open admissions
- ✓ISI 'Excellent' Educational Quality outcome (2022) plus CIS, Middle States and IBO accreditation
- ✓Pioneer IB credentials — adopted the IB as its main curriculum in 1979, among the first in England
- ✓Strong, consistent IB Diploma outcomes (37-point average, 100% pass rate, Class of 2025)
- ✓Small ~250-student, multi-nationality community giving high individual attention
- ✓Established girls' boarding option within a values-led Catholic RSHM ethos
Trade-offs
- !Ofsted rating is 'Good', not 'Outstanding', so it is not in the top inspection band
- !High fees (up to £39,640/year) place it among the more expensive London options
- !Split-site model (Chiswick primary/middle, Ealing Diploma College) rather than a single campus
- !No British (A-level/GCSE) or American track for families wanting a non-IB pathway
- !No IB Primary Years Programme — provision starts at age 11, so no early-years or primary pathway
- !Very small enrolment limits breadth of co-curricular and peer cohort scale
- !Premium fees (GBP 39,540 day / up to GBP 66,990 full boarding for 2026-27)
- !Single-curriculum (IB only) with no A-level or alternative-pathway fallback
Best Fit For
- • Internationally mobile families wanting a globally portable IB pathway
- • Multilingual households wanting their child's mother tongue actively maintained
- • Students who will sit the bilingual IB Diploma
- • Families seeking a non-selective school with a strong EAL on-ramp into English
- • Families seeking an all-girls, values-led Catholic education
- • Internationally mobile families wanting a recognised full IB Diploma pathway
- • Students aged 11+ who thrive in a small, close-knit cohort
- • Families needing girls' boarding (full, weekly or flexi) near London
University Placement
School-reported · not independently verified
School-reported, unverified: published higher-education destinations (2012–2025 dataset) include King's College London, UCL, Imperial College London, Warwick, Edinburgh, Manchester and Bristol in the UK, plus international destinations such as Bocconi, Sciences Po, McGill, University of Toronto, University of Chicago and Keio University.
School-reported, unverified: graduates are described as progressing to top-tier universities worldwide, with around a third earning a bilingual IB diploma (Class of 2025).
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Frequently Asked Questions
Should I choose International School of London or Marymount International School London?
International School of London is best for: Internationally mobile families wanting a globally portable IB pathway. Marymount International School London is best for: Families seeking an all-girls, values-led Catholic education. The right choice depends on target curriculum, budget, and family priorities — the two are not linearly comparable.
How do fees compare between International School of London and Marymount International School London?
International School of London: £24,630–£39,640/year (2026/2027, ages 3–17; figures incl. VAT where applicable). Marymount International School London: Day GBP 39,540/yr; full boarding GBP 66,990/yr (2026-27, incl. VAT). Verify against each school's own published fees; some figures are sourced from third-party aggregators.
What curricula do International School of London and Marymount International School London offer?
International School of London: IB. Marymount International School London: IB. International School of London inspection: Ofsted "Good". Marymount International School London inspection: Independent Schools Inspectorate (ISI) "Excellent".
Do International School of London or Marymount International School London offer boarding?
International School of London: day school only. Marymount International School London: offers boarding.
Questions parents ask
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 →