In this paper we investigate the link between the language in which pupils take the Programme for International Student Assessment (PISA) test and the scores they achieve in this assessment, focusing upon the case of Wales. Using five rounds of PISA data and an instrumental variable approach, we show how pupils who took the test in Welsh score around 0.3 standard deviations (30 PISA test points) lower in reading, mathematics and science than their peers who took the test in English. This finding is robust to different model specifications and statistical approaches. We argue that this may indicate that the academic performance of teenagers in Wales may be underestimated in PISA – particularly amongst those who take this test in Welsh.

中文翻译：

---

测试语言对 PISA 分数的影响。来自威尔士的新证据

在本文中，我们调查了学生参加国际学生评估计划 (PISA) 测试的语言与他们在该评估中取得的分数之间的联系，重点关注威尔士的案例。使用五轮 PISA 数据和工具变量方法，我们展示了参加威尔士语考试的学生在阅读、数学和科学方面的得分如何比参加英语考试的同龄人低 0.3 个标准差（30 个 PISA 考试点）。这一发现对不同的模型规范和统计方法是稳健的。我们认为，这可能表明威尔士青少年的学业成绩在 PISA 中可能被低估了——尤其是在威尔士参加这项考试的那些人中。