ISI is a Government approved inspectorate responsible for the inspection of Association independent schools. Schools in the Associations are ranked among the best in the world and educate more than half a million children in 1,200 schools. ISI also inspects private further education colleges and English language schools on behalf of the Home Office. Inspection is for the benefit of the pupils and students, and seeks to improve the quality and effectiveness of their education and care.

ISI inspects all provision in Association independent schools, including education, Early Years Foundation Stage settings and boarding welfare provision. ISI also inspects British international schools worldwide, including those seeking approval under the Department for Education scheme for British Schools Overseas.