It is for Ofqual as the independent regulator of qualifications to set criteria for the development by awarding bodies of GCSE assessments to a common standard. Working to those criteria awarding bodies can seek to adapt their exam specifications to meet the needs of different learners to whom they offer exams. It is for Ofqual to regulate the resulting qualifications.
Section 129 of the Apprenticeships, Skills, Children and Learning Act 2009 sets out the general duties of Ofqual. It requires Ofqual to have regard to the reasonable requirements of those who are seeking to obtain or who might reasonably be expected to seek to obtain regulated qualifications, including those with learning difficulties But it also makes it clear that speaking a different language to that from the language of the teaching or assessment does not itself constitute a learning difficulty.