The aim of this paper is to examine the different learning strategies among the students of primary and upper-secondary schools and their use by developing the different proficiencies of modern languages. This study will also try to clarify if and how these strategies differ between the students of primary and upper-secondary schools and what cognitive, metacognitive and social effective aspects lie beyond these differences. The data used in the presented paper is previous research made on different learning strategies and their use in the modern language education in primary and upper secondary schools. This paper also uses a number of interviews with the pupils from primary and upper-secondary schools in order to illustrate if and how the use of their strategies differs and what aspects contribute to this difference.