Marymount International School London vs Southbank International School
🇬🇧 London · Side-by-side comparison on verifiable public data.
Both carry a public inspection verdict: Marymount International School London is Independent Schools Inspectorate (ISI) "Excellent" and Southbank International School is Independent Schools Inspectorate (ISI) "Met all standards (2024-2025, post-2023 framework)" — 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
| Marymount International School London | Southbank International School | |
|---|---|---|
| Curriculum | IB | IB |
| Ages | 11-18 | 2-18 |
| Languages of instruction | English | English |
| Annual fees | Day GBP 39,540/yr; full boarding GBP 66,990/yr (2026-27, incl. VAT) | £6,724-£16,033 per term (2025/26 Early Childhood half-day to DP; 2026/27 DP up to £16,033) |
| Enrollment | 250 | 800 |
| Boarding | Yes | Day only |
| Inspection rating | Independent Schools Inspectorate (ISI): Excellent | Independent Schools Inspectorate (ISI): Met all standards (2024-2025, post-2023 framework) |
| Accreditations | Council of International Schools (CIS), Middle States Association of Colleges and Schools, International Baccalaureate Organisation (IBO) | IB World School (PYP, MYP, DP), Independent Schools Association (ISA) member, ISI-inspected independent school |
Strengths
- ✓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
- ✓Full IB continuum (PYP, MYP, DP) authorised end-to-end, ages 2-18, within one school
- ✓Strong published DP outcomes: Class of 2025 average of 35.4 against a 30.58 global average, with three perfect 45 scores
- ✓Highly international community of around 70 nationalities reinforcing genuine international-mindedness
- ✓Embedded EAL support enabling students with little or no English to access PYP and MYP
- ✓Central-London campuses across Hampstead, Kensington and Westminster offering catchment flexibility
Trade-offs
- !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
- !Premium fees, with DP at up to £16,033 per term inc. VAT for 2026/27 plus deposit and capital charges
- !Recent ISI inspections use a met / not-met framework, so no top graded band evidences excellence
- !Programmes split across separate campuses rather than one continuous all-through site
- !Day-only school with no boarding provision
Best Fit For
- • 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
- • Internationally mobile families wanting a single IB pathway from age 2 to 18
- • Students who thrive in a multilingual, multinational peer group
- • Families targeting strong IB Diploma results for university entry
- • Children needing structured EAL support to enter an English-medium programme
University Placement
School-reported · not independently verified
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).
School-reported, unverified: Southbank describes itself as 'London's leading International Baccalaureate (IB) School' and reports three Class of 2025 students scoring a perfect 45, placing them in the top 1% globally.
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Frequently Asked Questions
Should I choose Marymount International School London or Southbank International School?
Marymount International School London is best for: Families seeking an all-girls, values-led Catholic education. Southbank International School is best for: Internationally mobile families wanting a single IB pathway from age 2 to 18. The right choice depends on target curriculum, budget, and family priorities — the two are not linearly comparable.
How do fees compare between Marymount International School London and Southbank International School?
Marymount International School London: Day GBP 39,540/yr; full boarding GBP 66,990/yr (2026-27, incl. VAT). Southbank International School: £6,724-£16,033 per term (2025/26 Early Childhood half-day to DP; 2026/27 DP up to £16,033). Verify against each school's own published fees; some figures are sourced from third-party aggregators.
What curricula do Marymount International School London and Southbank International School offer?
Marymount International School London: IB. Southbank International School: IB. Marymount International School London inspection: Independent Schools Inspectorate (ISI) "Excellent". Southbank International School inspection: Independent Schools Inspectorate (ISI) "Met all standards (2024-2025, post-2023 framework)".
Do Marymount International School London or Southbank International School offer boarding?
Marymount International School London: offers boarding. Southbank International School: day school only.
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 →