This thesis explores the consequences of linguistic choices for quality education, selfdetermined development and children's rights in education. The analysis centers on a case study of a curriculum change in Zanzibar in which English has replaced Kiswahili as the language of instruction in the last year of primary school in Mathematics and Science subjects. The case study is grounded in an extensive review of theory and practices on the relationship between Language of instruction, learning and rights in education. The research design encompassed several field visits to Zanzibar over a period of three years, and deployed qualitative methods, including observation in classrooms and an extensive set of interviews with policy makers, teachers and Tanzanian academics. The field study researched the reasons behind the curriculum change, the extent to which schools were prepared for the change, and the consequences of the change for the learning environment. The research findings have been presented and discussed in the four papers constituting this thesis and elaborated in the kappa (extended abstract). In making the curriculum change, Zanzibari policy makers have been influenced by the still powerful notion throughout Africa that learning in a Western language will promote development and modernization. This is reinforced in development aid programs directed at the educational section, many of which encourage and support the use of a nonlocal Language of Instruction. However, in the Zanzibari case, neither teacher preparation nor support materials in the form of books, teaching plans and teacher training have been robust enough to support the curriculum change. It was found that teachers are not fluent enough in English to master teaching in accordance with the new curriculum. Given the deterioration of the learning environment attributable to the replacement of Kiswahili with English and the lack of adequate support, the author's assessment is that the capacity for the curriculum to enable quality learning has been reduced. From the perspective of a rights-capability-based approach, this curriculum change violates Zanzibari children's right in education. Local languages need to be valued in education in order that children will be prepared for engaging with the world in a language they understand
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