To get a Child Student visa without any problems, the curriculum of a British independent school must comply with:
National educational program – educational standards for state-funded schools. Independent schools must provide the same number of compulsory subjects according to the national standard. At the same time, they don’t have to stick to state programs and can offer additional subjects or teach compulsory subjects more thoroughly.
Independent Schools Inspectorate (ISI) – standards controlling British independent schools.
Regulated Qualifications Framework (RQF) (level 3 or below) that assesses independent school curriculum in terms of amount and complexity of the provided knowledge.
When you start your course in the UK, you can take a special preparatory course. It allows to improve the level of English and avoid problems with further studies.