This chapter summarizes the findings of 32 years of research from all of our longitudinal studies to date, conducted in 36 school districts in 16 U.S. states, more than 7.5 million student records analyzed, following English learners (of all language backgrounds) as far as Grades K–12. These studies are very generalizable to all regions and contexts of the United States and have been replicated in other countries, answering questions regarding program effectiveness for policymakers in education. We have shown that English-only and transitional bilingual programs of short duration only close about half of the achievement gap between English learners and native English speakers, while high-quality, long-term bilingual programs close all of the gap after 5–6 years of schooling through the students’ first and second languages (L1 and L2). In addition, our studies answer the linguistic question of how long it takes student groups to reach grade-level achievement in their L2, and we have developed and refined our theoretical Prism model by collecting and analyzing program effectiveness data, basing the Prism model on our empirical findings.

中文翻译：

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验证双语教育的力量：32 年的大规模纵向研究

本章总结了迄今为止我们所有纵向研究的 32 年研究结果，这些研究在美国 16 个州的 36 个学区进行，分析了超过 750 万个学生记录，跟踪英语学习者（所有语言背景）直至年级K-12。这些研究非常适用于美国的所有地区和背景，并已在其他国家复制，回答了有关教育决策者计划有效性的问题。我们已经表明，短期的纯英语和过渡性双语课程只能缩小英语学习者和以英语为母语的人之间成绩差距的一半左右，而高质量、长期的双语课程在 5-6 年后缩小所有差距通过学生的第一语言和第二语言（L1 和 L2）进行学校教育。此外，