The United Kingdom government website Check if you need a visa says that high-school students (aged 17 and under) coming to study in the UK from Europe for six months or more at an Independent School, require a Child Student visa and sponsorship from an "accredited institution". It then mentions a list of the routes to accreditation. These include being "listed" by Ofsted or the Independent Schools Inspectorate (ISI).
Ofsted will inspect and report on schools, and can give a school a rating from "inadequate" through "requires improvement" to "good" and "outstanding". For independent schools, the report will also state separately if the school meets the Independent School Standards.
If a school is inspected by Ofsted, and is found to be "requires improvement" or "inadequate", does it lose its listing and accreditation for visa purposes? If it does not meet the Independent School Standards, does it lose accreditation? Or does "listed" include schools with poor Ofsted or ISS reports?