SEK International School - El Castillo

The SEK group's largest Madrid campus, set on 40,000 square metres in Villanueva de la Canada and one of the few Spanish schools that still runs full boarding. The first school in Spain to join the IB, in 1977.

Opened for the 1972-73 year and authorised for the IB Diploma in 1977. The campus runs the full IB continuum (PYP, MYP, DP) for ages 4 months to 18, with separate buildings per age group on a wooded site northwest of Madrid. Boarding houses take around 93 boys and 34 girls, mostly from Spanish families outside Madrid and a smaller international cohort.

The IB results are consistently among the strongest in Spain, with several students annually scoring 45 and around a fifth of the cohort breaking 40. Parents describe a school that feels institutional in scale rather than intimate, which suits families who value breadth, sports, and the boarding option. The architecture itself won a UNESCO award in 1974, which is unusual flag-planting for a private school.

• Independent parent prose for El Castillo is thin online; most third-party material describes the campus as the boarding flagship of the SEK group, not parent-voice reviews.
• Discussion that does surface treats SEK as a group: a Madrid-school review thread from a former 1990s student calls SEK schools conservative-Christian in tone but less restrictive than nearby Opus Dei schools.
• One former staff member spent five years at El Castillo and calls it a good Madrid choice; this is the only insider voice in the recent record.
• Football fans cite the campus as the school where Luka Doncic studied and passed Spanish bachillerato exams, which is interesting but not a parent signal.