Teacher professional development (PD) is seen as a promising intervention to improve teacher knowledge, instructional practice, and ultimately student learning. While research finds instances of significant program effects on teacher knowledge, little is known about how long these effects last. If teachers forget what is learned, the contribution of the intervention will be diminished. Using a large-scale data set, this study examines the sustainability of gains in teachers’ content knowledge for teaching mathematics (CKT-M). Results show that there is a negative rate of change in CKT after teachers complete the training, suggesting that the average score gain from the program is lost in just 37 days. There is, however, variation in how quickly knowledge is lost, with teachers participating in summer programs losing more rapidly than those who attend programs that occur during school years. The implications of these findings on designing and evaluating PD programs are discussed.

中文翻译：

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教师学习持续吗？了解有多少教师在专业发展后保留了他们的知识

教师专业发展 (PD) 被视为一种有前景的干预措施，可提高教师知识、教学实践和最终学生学习。虽然研究发现了项目对教师知识产生重大影响的实例，但人们对这些影响持续多长时间知之甚少。如果教师忘记所学，干预的作用就会减弱。本研究使用大规模数据集检验教师数学教学内容知识 (CKT-M) 获得的可持续性。结果表明，教师完成培训后 CKT 的变化率为负，这表明该计划的平均分数增长仅在 37 天内就消失了。然而，知识丢失的速度存在差异，参加暑期课程的教师比参加学年课程的教师流失得更快。讨论了这些发现对设计和评估 PD 计划的影响。