This thesis consists of three empirical studies. The first study, Rationales to Language-in-Education Policies in Postcolonial Africa: Towards a Holistic Approach, considers two issues. First, it explores the factors affecting the choice of an LiE policy in 35 African countries. The results show that the countries adopting a unilingual education system put different weights on the influential parameters than countries adopting a bilingual education system. Second, the study investigates how decision makers can ensure the optimal choice of language(s) of instruction by developing a non-cooperative game theoretic model with network externalities. The model shows that it is never optimal for two countries to become bilingual, or for the majority linguistic group to learn the language of the minority group, unless there is minimum cooperation to ensure an equitable redistribution of payoffs. The second study, The Role of Language in Learning Achievement: A Namibian Case Study, investigates the role played by home language and language proficiency on SACMEQ II mathematics scores of Namibian Grade-6 learners. HLM is used to partition the total variance in mathematics achievement into its within- and between-school components. Results show that although home language plays a limited role in explaining within- and between-school variations in mathematics achievement, language proficiency (proxied by reading scores) plays a significant role in the heterogeneity of results. Finally, the third study, Language Skills and Economic Returns, investigates the economic returns to language skills, assuming that language competencies constitute key components of human capital. It presents results from eight IALS countries. The study finds that in each country, skills in a second language are a significant factor that constrains wage opportunities positively.

L’Angola est un contexte encore relativement méconnu quelque soit la discipline en sciences sociales. Pour la didactique des langues et des cultures, cette situation de départ prête à questionner l’approche – ou les approches – à adopter pour mener la recherche. Cette thèse propose de vérifier la pertinence d’une approche plurielle faisant appel à l’histoire et à deux grands axes de travail : l’axe diachronique-synchronique et l’axe micro-macro. L’objectif majeur est de mettre à profit cette approche pour : (1) pallier le manque de données indispensables à la compréhension de la singularité du contexte sociolinguistique contemporain et au développement de politiques linguistiques et éducatives adaptées ; (2) déterminer de manière historicisée les caractéristiques du système éducatif et de la culture éducative actuels ; (3) proposer des pistes d’application pour améliorer les conditions d’enseignement / apprentissage en langue et des langues. La première partie de cette thèse explicite les objectifs et les hypothèses de recherche (chapitre 1), expose les éléments généraux concernant le contexte national (chapitre 2) puis les concepts mobilisés pour la réflexion et l’analyse (chapitre 3). La seconde partie fournit des éléments descriptifs, explicatifs et analytiques jusqu’alors inédits concernant le contexte de cette recherche : un cadre historique (chapitre 4), un cadre sociolinguistique (chapitre 5) et un focus construit autour de la langue française en Angola dont découle une réflexion plus générale sur le système éducatif public contemporain (chapitre 6). À partir de l’analyse de trois corpus didactiques sélectionnés à partir de leur date de production (1962, 1980 et 2005), la troisième partie permet de mettre à profit les apports des deux premières parties pour effectuer une analyse de corpus historicisée visant à mettre au jour les caractéristiques de la didactisation en fonction des époques et les traces de ce processus dans les productions didactiques contemporaines. / Angola remains a relatively unknown context, regardless of the discipline in the social sciences. For the didactics of languages and cultures, this baseline situation raises the question of the approach - or the approaches - to adopt in order to conduct research. This thesis proposes to examine the relevance of a plural approach calling upon history and involving two major lines of work: the diachronic-synchronic axis and the micro-macro axis. The major objective is to build on this approach to: (1) fill in for the lack of data that are essential to understand the singularity of the contemporary sociolinguistic context, and to develop adequate language and education policies; (2) determine, using historicization, the characteristics of the education system and the current educational culture; (3) propose implementing strategies to improve the teaching / learning in language and of languages. The first part of this thesis clarifies the research objectives and hypotheses (Chapter 1), presents the general elements defining the national context (Chapter 2), as well as the concepts mobilized for reflection and analysis (Chapter 3). The second part provides descriptive, explanatory and analytical elements hitherto unpublished regarding the context of this research: a historical background/context (Chapter 4), a sociolinguistic framework (Chapter 5) and a focus built around the French language in Angola leading to a broader reflection on the contemporary public education system (chapter 6). Based on the analysis of three teaching corpus selected following their date of production (1962, 1980 and 2005), the third part allows to exploit the findings made in the first two sections, in order to perform historicised corpus analysis aimed at revealing the characteristics of didactization over time, as well as the traces of this process in contemporary educational productions. / Angola ainda é um contexto relativamente desconhecido, qualquer que seja a disciplina nas ciências sociais. Para a didática das línguas e culturas, esta situação inicial se presta a questionar a abordagem - ou as abordagens - a adoptar para realizar a pesquisa. Esta tese propõe a verificar a relevância de uma abordagem multifacetada que envolva história e duas linhas principais de trabalho: o eixo diacrónico-sincrônico e o eixo micro-macro. O objetivo principal é de tirar partido dessa abordagem para: (1) superar a falta de dados essenciais para a compreensão da singularidade do contexto sociolinguístico contemporâneo e para o desenvolvimento de políticas linguísticas e educativas adequadas; (2) determinar de modo historizado as características do sistema de educação e da cultura educacional vigente; (3) propor formas de aplicação para melhorar o ensino / aprendizagem na linguagem e das línguas. A primeira parte desta tese explícita os objectivos e as hipóteses de investigação (Capítulo 1), define os itens gerais sobre o contexto nacional (Capítulo 2) e os conceitos mobilizados para reflexão e análise (Capítulo 3). A segunda parte fornece elementos descritivos, explicativos e analíticos inéditos a respeito do contexto desta pesquisa: um cenário histórico (Capítulo 4), um quadro sociolinguístico (Capítulo 5) e um foco construído em torno da língua francesa em Angola que segue uma reflexão mais geral sobre o sistema educativo público contemporâneo (capítulo 6). A partir da análise de três corpus didáticos selecionados segundo a data de produção (1962, 1980 e 2005), a terceira parte permite alavancar as contribuições das duas primeiras partes para realizar a análise de corpus historizada no objetivo de descobrir as características da didatização com os tempos e vestígios de este processo em produções educacionais contemporâneas.