In recent years, many countries have experienced a significant expansion of higher education enrolment. There is a particular interest among policy makers for further growth in STEM subjects, which could lead to larger classes in these fields. This study estimates the effect of class size on academic performance of university students, distinguishing between STEM and non-STEM fields. Using administrative data from a large UK higher education institution, we consider a sample of 25,000 students and a total of more than 190,000 observations, spanning seven cohorts of first-year undergraduate students across all disciplines. Our identification of the class size effects rests on within student-across course variation, thus controlling for any unobservable difference across students, albeit other forms of bias stemming from selection of elective courses may still be present. Overall, we find that larger classes are associated with significantly lower grades (effect size of −0.08). This overall effect masks considerable differences across academic fields, as we find a larger effect in STEM subjects (−0.11) than in non-STEM subjects (−0.04). We further explore the heterogeneity of the effect along the dimensions of students’ socio-economic status, ability, and gender, finding that smaller classes are particularly beneficial for students from a low socio-economic background, and within STEM fields for higher ability and male students.

近年来，许多国家都经历了高等教育入学人数的显着增加。决策者特别关注STEM学科的进一步发展，这可能会导致这些领域的学生人数更多。本研究通过区分STEM和非STEM领域来估计班级规模对大学生学习成绩的影响。我们使用来自英国一家大型高等教育机构的行政数据，对25,000名学生的样本和总计190,000多个观察值进行了分析，涵盖了所有学科的7个一年级本科生队列。我们确定班级规模的影响在于学生跨课程的差异，从而控制学生之间任何不可观察的差异，尽管选修课程的选择可能还会产生其他形式的偏见。总体而言，我们发现较大的类别与较低的等级相关（效果大小为-0.08）。这种总体效果掩盖了各个学术领域的显着差异，因为我们发现STEM科目（-0.11）的影响要大于非STEM科目（-0.04）的影响。我们进一步研究了学生在社会经济地位，能力和性别方面的异质性，发现较小的班级对社会经济背景较低的学生特别有益，而在STEM领域内对于能力和男性较高的学生特别有利学生们。这种总体效果掩盖了各个学术领域的显着差异，因为我们发现STEM科目（-0.11）的影响要大于非STEM科目（-0.04）的影响。我们进一步研究了学生在社会经济地位，能力和性别方面的异质性，发现较小的班级对社会经济背景较低的学生特别有益，而在STEM领域内对于能力和男性较高的学生特别有利学生们。这种总体效果掩盖了各个学术领域的显着差异，因为我们发现STEM科目（-0.11）的影响要大于非STEM科目（-0.04）的影响。我们进一步研究了学生在社会经济地位，能力和性别方面的异质性，发现较小的班级对社会经济背景较低的学生特别有益，而在STEM领域内对于能力和男性较高的学生特别有利学生们。