Multigrading represents the practice of mixing children of different ages in the same classroom. This paper examines the effect of attending a multigrade class in Grade 2 on students’ academic achievement in Grades 2, 5, and 8, respectively, considering Italy as a case study. To address the issue of endogeneity of multigrading (and class size), we adopt an IV identification strategy based on a law that disciplines class composition. We show that multigrading has a positive (16 percent of a standard deviation) short-term effect on academic achievements. However, this effect diminishes over time and becomes negative (-10 percent of a standard deviation) if students spend several years in a multigrade class. Mechanism analysis indicates the fundamental role of teachers and suggests that the negative long-term effect of multigrading is not statistically different from zero when multigrade classes are taught by more experienced teachers. These findings, based on longitudinal data, reconcile contrasting results in the literature, which are based on cross-sectional data and on the short-term effects of multigrading.

多年级是指将不同年龄的孩子混合在同一教室的做法。本文以意大利为例，探讨了二年级参加多年级课程对二年级、五年级和八年级学生学业成绩的影响。为了解决多分级（和班级规模）的内生性问题，我们采用基于班级构成规律的 IV 识别策略。我们表明，多评分对学业成绩具有积极的短期影响（标准差为 16%）。然而，如果学生在多年级班级中度过数年，这种影响会随着时间的推移而减弱，并变为负值（标准差的-10%）。机制分析表明了教师的基本作用，并表明当多年级课程由更有经验的教师教授时，多年级的负面长期影响在统计上与零没有什么不同。这些基于纵向数据的发现与文献中基于横截面数据和多分级的短期影响的对比结果相一致。