Halcyon London International School vs Marymount International School London
🇬🇧 London · Side-by-side comparison on verifiable public data.
Both carry a public inspection verdict: Halcyon London International School is Independent Schools Inspectorate (ISI) "Met all standards (2024 routine, 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. 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
| Halcyon London International School | Marymount International School London | |
|---|---|---|
| Curriculum | IB | IB |
| Ages | 11-18 | 11-18 |
| Languages of instruction | English | English |
| Annual fees | £41,040-£42,912/year incl. VAT (2026/27) | Day GBP 39,540/yr; full boarding GBP 66,990/yr (2026-27, incl. VAT) |
| Enrollment | 172 | 250 |
| Boarding | Day only | Yes |
| Inspection rating | Independent Schools Inspectorate (ISI): Met all standards (2024 routine, post-2023 framework) | Independent Schools Inspectorate (ISI): Excellent |
| Accreditations | IB World School, ISI-inspected (DfE-regulated) | Council of International Schools (CIS), Middle States Association of Colleges and Schools, International Baccalaureate Organisation (IBO) |
Strengths
- ✓IB Diploma average of 35 for the Class of 2025, above both UK and world averages, with recent perfect scores of 45
- ✓Continuous, focused IB pathway (MYP then DP) delivered by subject specialists with strong inquiry-led teaching
- ✓Small, intimate community (around 172 pupils) enabling close staff-pupil relationships and individual learning mentors
- ✓Genuinely international, largely bilingual student body with a strong inclusion, diversity and global-citizenship culture
- ✓Innovation-led ethos, including documented integration of artificial intelligence into the curriculum
- ✓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
- !Limited on-site sport and outdoor space; inspectors asked leaders to extend outdoor and physical-skills opportunities
- !Operates within a shared, leased central-London building rather than a self-contained campus
- !Young school (opened 2013) with a comparatively short track record
- !Small scale and secondary-only remit limit breadth of facilities, cohort size, and alumni network versus larger London internationals
- !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 an unbroken IB MYP-to-Diploma route in central London
- • Bilingual or multilingual students, including those targeting the IB bilingual diploma
- • Families who value a small, close-knit, innovation-led environment over a large traditional campus
- • Students who thrive on inquiry-based learning rather than a GCSE/A-level track
- • 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: the Class of 2025 saw graduates progress to Russell Group universities and to specialist art, music and drama colleges in the UK and internationally.
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 Halcyon London International School or Marymount International School London?
Halcyon London International School is best for: Internationally mobile families wanting an unbroken IB MYP-to-Diploma route in central London. 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 Halcyon London International School and Marymount International School London?
Halcyon London International School: £41,040-£42,912/year incl. VAT (2026/27). 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 Halcyon London International School and Marymount International School London offer?
Halcyon London International School: IB. Marymount International School London: IB. Halcyon London International School inspection: Independent Schools Inspectorate (ISI) "Met all standards (2024 routine, post-2023 framework)". Marymount International School London inspection: Independent Schools Inspectorate (ISI) "Excellent".
Do Halcyon London International School or Marymount International School London offer boarding?
Halcyon London International School: 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 →