Erasmus+ supports inter-European exchanges for many students each year. The participants were asked to take a pre- and posttest with online language support (OLS). The study measured students' English development via OLS pre- and posttest scores from 2015-2021. Mixed methods with an explanatory-sequential design were utilized in this research. This study demonstrated a notable enhancement in students' test scores within competency levels B1-B2. Integration through joint display analysis helped clarify the quantitative results. Practical and theoretical implications of student exchange programs for language improvement, including length of stay, interaction, and self-confidence, are presented.