This chapter deals with the challenges of one specific set of high-stakes tests in a national environment: the measurement of language ability in what are known in South Africa as "home languages" at the exit level of secondary school. It describes the constitutional, legal and administrative framework within which these assessments of language ability are to be conducted. The chapter makes a number of observations as regards the challenges of offering instruction "home languages" in an urbanizing environment, problematizing the very notion of "home language". It identifies the variation in the high-stakes assessment of a diversity of languages, which is not only unacceptable but unfair, mainly because of the differential subsequent impact it has on different groups of learners. The chapter concludes with a consideration of the appropriateness of the public provision of language instruction at school, which refers to its contextual or ecological validity.