Marymount International School London vs Southbank International School
🇬🇧 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 (Marymount International School London: Independent Schools Inspectorate (ISI) "Excellent"; Southbank International School: Independent Schools Inspectorate (ISI) "Met all standards (2024-2025, post-2023 framework)") you can compare directly; Marymount International School London offers boarding while the other is day-only. 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: 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.
More Comparisons
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 →