ACS International Schools vs Marymount International School London
🇬🇧 London · Side-by-side comparison on verifiable public data.
Reviewed by Priscilla Han
Which should you choose?
Both run IB, so the difference is inspection rating, boarding, and fees rather than the curriculum itself; both carry a public inspection verdict (ACS International Schools: Independent Schools Inspectorate (ISI) "Met all standards (2025 EQI, post-2023 framework)"; Marymount International School London: Independent Schools Inspectorate (ISI) "Excellent") you can compare directly. The choice comes down to target curriculum, whether you need boarding, and budget — verify fees against each school's own figures.
Both carry a public inspection verdict: ACS International Schools is Independent Schools Inspectorate (ISI) "Met all standards (2025 EQI, post-2023 framework)" 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. On cost, ACS International Schools has the noticeably lower entry fee — a material difference for budget-conscious families. See the table below for the figures, and verify against each school's own published fees.
Key Facts
| ACS International Schools | Marymount International School London | |
|---|---|---|
| Curriculum | American / IB | IB |
| Ages | 2-18 (Cobham); 3-18 (Egham, Hillingdon) | 11-18 |
| Languages of instruction | English | English |
| Annual fees | ACS Cobham 2026-2027 day tuition GBP 9,950-39,960/yr; 7-day boarding (Grades 8-12) up to GBP 69,060/yr inclusive | Day GBP 39,540/yr; full boarding GBP 66,990/yr (2026-27, incl. VAT) |
| Enrollment | 2,200 | 250 |
| Boarding | Yes | Yes |
| Inspection rating | Independent Schools Inspectorate (ISI): Met all standards (2025 EQI, post-2023 framework) | Independent Schools Inspectorate (ISI): Excellent |
| Accreditations | New England Association of Schools and Colleges (NEASC), College Board, International Baccalaureate Organization, Educational Collaborative for International Schools (ECIS), Independent Schools Association (ISA) | Council of International Schools (CIS), Middle States Association of Colleges and Schools, International Baccalaureate Organisation (IBO) |
Strengths
- ✓Dual American (High School Diploma plus AP) and IB pathways under one operator, rare in the London market
- ✓ACS Egham offers all four IB programmes (PYP, MYP, DP, CP) - a full through-IB continuum
- ✓Highly international community of 70+ nationalities with structured EAL and home-language support
- ✓Long-established (since 1967) with NEASC accreditation and College Board / IB partnerships
- ✓Boarding available at Cobham (Grades 8-12), including flexible temporary boarding options
- ✓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
- !Premium fees, with senior-year day tuition near GBP 40,000 and full boarding around GBP 69,000 a year at Cobham
- !IB continuum breadth (all four programmes) is concentrated at Egham, not uniform across all three campuses
- !IGCSE is not offered, so families wanting a British GCSE route are not served
- !Current ISI framework yields a 'met all standards' outcome rather than a published top graded band
- !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 US diploma plus AP and/or IB pathway
- • Students targeting US university applications who value AP and a transcript-based diploma
- • Families needing boarding within commuting distance of London (Cobham)
- • Children needing EAL support within a multinational peer group
- • 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: ACS promotes US and international university destinations across its alumni, but no independently verified placement figures were found.
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).
More Comparisons
Frequently Asked Questions
Should I choose ACS International Schools or Marymount International School London?
ACS International Schools is best for: Internationally mobile families wanting a US diploma plus AP and/or 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 ACS International Schools and Marymount International School London?
ACS International Schools: ACS Cobham 2026-2027 day tuition GBP 9,950-39,960/yr; 7-day boarding (Grades 8-12) up to GBP 69,060/yr inclusive. 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 ACS International Schools and Marymount International School London offer?
ACS International Schools: American, IB. Marymount International School London: IB. ACS International Schools inspection: Independent Schools Inspectorate (ISI) "Met all standards (2025 EQI, post-2023 framework)". Marymount International School London inspection: Independent Schools Inspectorate (ISI) "Excellent".
Do ACS International Schools or Marymount International School London offer boarding?
ACS International Schools: offers boarding. 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 →