Many students are currently being taught in a language in which they are not confident and this impacts on both their learning outcomes and experiences. This is the situation in Tanzania where secondary schooling is delivered in English, after seven years of primary schooling during which teachers and students use Kiswahili, the national language and "lingua franca." Recognising that the current situation will remain for the foreseeable future, this research looks at the student experience in two secondary schools in the Morogoro region of Tanzania. It takes an ethnographic approach, with a view to developing an in-depth and more nuanced understanding of the challenges faced by pupils who are learning in a language in which they are not fluent. After outlining the current language situation in schools, this report identifies six factors that influence students' ability to learn English and to learn using English as the medium of instruction: the lack of an environment that supports language learning; low student confidence and fear of making mistakes; peer relationships and support; parental resources and students' language foundation; government policy and resource provision; and out-of-school challenges that affect learning. Ultimately, this report supports those who call for a shift to use Kiswahili as the language of instruction throughout the education system, alongside good quality English language teaching. It concludes with recommendations for Tanzanian government policymakers and practitioners.