Schools have a duty to deliver the National Curriculum to children. In certain circumstances however such a when a child is educated within a pupil referral unit that duty does not apply.
Following the passage of the Human Rights Act 1998 parents have the right to expect their religious and philosophical convictions respected by the LEA.
In some circumstances a child may be disapplied from a National Curriculum subject. This may for example be in situations where a child has a language disorder, and thus it might be too much to expect them to learn a language in addition to English.