Increasing access to education may have consequences that go beyond effects on marginal students encouraged to enroll. It may change peer effects, school quality, and returns to skill. This paper studies how classmates and teaching inputs affect learning of university students, exploiting an educational expansion in Italian STEM majors. Newly collected data on 27,236 students indicate that less prepared classmates and congestion of teaching resources lowered learning of incumbent students in STEM fields. Their learning, however, increased in courses in which the new classmates raised average preparedness. These effects might have had long-lasting consequences on the returns to STEM degrees.

中文翻译：

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教育扩展的间接影响：来自大学专业的大幅度招生的证据

受教育的机会增加，其后果可能超出对鼓励入学的边缘学生的影响。它可能会改变同伴的影响，学校的质量并恢复技能。本文研究了同学和教学投入如何影响大学生的学习，并利用了意大利STEM专业的教育扩展。最新收集的27,236名学生的数据表明，准备不足的同学和教学资源的拥挤降低了STEM领域在职学生的学习。但是，在新同学提高平均备考水平的课程中，他们的学习有所增加。这些影响可能会对STEM度的回报产生长期影响。