The effect of the language of instruction on academic performance
利用博尔扎诺自由大学的学生数据，研究发现用第二语言参加考试会导致成绩下降约9.5%，即使语言熟练度较高也无法完全消除这一损失。
Education in a language other than the mother tongue is common. This is increasingly relevant in tertiary education, due to the growing international mobility of students. While the advantages of foreign language skills on the labour market are well-studied, literature on the cost of non-native learning is still not well established. To fill this gap, we explore the impact of the language of instruction on grades by using administrative data provided by the Free University of Bozen-Bolzano. We exploit the fact that students whose mother tongue is for the most part Italian or German learn and take exams in English, German, and Italian. Our results, controlling for student fixed effects, show that taking an exam in a second language leads to a loss in grade points of approximately 9.5% (or 0.22 within-student standard deviations). These results are confirmed relying on an identification strategy that leverages on course language assignments in the standard study plan, circumventing the potential non-compliance of students selecting out of languages other than the mother tongue. A high proficiency in the non-native language mitigates - but does not eliminate - the loss. Moreover, also the number of failed attempts increases.