ACS International Schools vs Halcyon London 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 (ACS International Schools: Independent Schools Inspectorate (ISI) "Met all standards (2025 EQI, post-2023 framework)"; Halcyon London International School: Independent Schools Inspectorate (ISI) "Met all standards (2024 routine, post-2023 framework)") you can compare directly; ACS International Schools 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: ACS International Schools is Independent Schools Inspectorate (ISI) "Met all standards (2025 EQI, post-2023 framework)" and Halcyon London International School is Independent Schools Inspectorate (ISI) "Met all standards (2024 routine, post-2023 framework)" — a rare pairing where an official quality rating can be compared head-to-head. One practical difference: ACS International Schools 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
| ACS International Schools | Halcyon London International School | |
|---|---|---|
| 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 | £41,040-£42,912/year incl. VAT (2026/27) |
| Enrollment | 2,200 | 172 |
| Boarding | Yes | Day only |
| Inspection rating | Independent Schools Inspectorate (ISI): Met all standards (2025 EQI, post-2023 framework) | Independent Schools Inspectorate (ISI): Met all standards (2024 routine, post-2023 framework) |
| Accreditations | New England Association of Schools and Colleges (NEASC), College Board, International Baccalaureate Organization, Educational Collaborative for International Schools (ECIS), Independent Schools Association (ISA) | IB World School, ISI-inspected (DfE-regulated) |
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
- ✓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
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
- !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
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
- • 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
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: the Class of 2025 saw graduates progress to Russell Group universities and to specialist art, music and drama colleges in the UK and internationally.
More Comparisons
Frequently Asked Questions
Should I choose ACS International Schools or Halcyon London International School?
ACS International Schools is best for: Internationally mobile families wanting a US diploma plus AP and/or IB pathway. Halcyon London International School is best for: Internationally mobile families wanting an unbroken IB MYP-to-Diploma route in central London. 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 Halcyon London International School?
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. Halcyon London International School: £41,040-£42,912/year incl. VAT (2026/27). Verify against each school's own published fees; some figures are sourced from third-party aggregators.
What curricula do ACS International Schools and Halcyon London International School offer?
ACS International Schools: American, IB. Halcyon London International School: IB. ACS International Schools inspection: Independent Schools Inspectorate (ISI) "Met all standards (2025 EQI, post-2023 framework)". Halcyon London International School inspection: Independent Schools Inspectorate (ISI) "Met all standards (2024 routine, post-2023 framework)".
Do ACS International Schools or Halcyon London International School offer boarding?
ACS International Schools: offers boarding. Halcyon London 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 →