Halcyon London International School 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 (Halcyon London International School: Independent Schools Inspectorate (ISI) "Met all standards (2024 routine, post-2023 framework)"; Marymount International School London: Independent Schools Inspectorate (ISI) "Excellent") 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: 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).
More Comparisons
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 →