This article presents a study on the evaluation of the language skills of pupils in 5th fundamental year in Burundi in Mathematics. The behavioural indices of the pupils in oral and written comprehension and expression revealed that their main weaknesses were in oral and written expression. In the absence of oral formulation of their own ideas, some pupils limited themselves to answering in one word or in incomplete sentences while others preferred to remain silent or to express themselves in Kirundi. In listening comprehension, they had no problem. They answered the questions and performed the tasks they had been given orally in French. In reading comprehension, they also managed to appropriate the useful information read.