The Senior School incorporates Grades 9 to 12, when students are typically aged between 14 and 18.

The Senior School has strong academic focus, as students follow IGCSE courses in Grades 9 and 10, before embarking on A levels in Grades 11 and 12. A prominent University Guidance Counselling team, supported by globally experienced teaching staff, who themselves attended world-leading colleges, helps senior school students to identify and achieve offers from outstanding international universities.

IGCSE Courses run throughout Grade 9 and 10 with final examinations taking place in the summer of Grade 10. International Harrovians typically sit a core set of IGCSEs in English, Maths, Chemistry, Physics, Biology and Global Perspectives, adding a further four subjects chosen from Art, Business, Computer Science, Design and Technology, Drama, Economics, Geography, History, Music, Psychology and Modern Foreign Languages.

During Grades 11 and 12, students follow A levels with final examinations in the summer of Grade 12. Harrovians taking A levels typically select three or four A levels, chosen from the wide selection of subjects offered at IGCSE.