There is no requirement for home educated children to sit national tests. Section 7 of the Education Act 1996 requires parents to make sure that their child receives an efficient, full-time education which is suitable to the age, ability and aptitudes of the child, and any special educational needs. Parents have wide discretion as to the content of that education and how it is taught. They are not required to follow the National Curriculum, to which the key stage tests are linked.
Children attending school are not legally required to sit the national key stage tests, although most children in state-funded schools and some independent schools do take them.