• Program typologies and immersion-based designs unify bilingual education research, spanning typologies, St. Lambert experiments, and Culver City immersion, reflecting how program structure shapes outcomes across communities [2], [3], [7], [10], [17], [19], [20].

• Cognitive-psycholinguistic mechanisms and transfer between L1 and L2 emerge as a core research thread, linking first/second language analogies, cognitive consequences of bilingual schooling, motivation, strategy use, and error development across several studies [1], [6], [9], [11], [13], [15], [16].

• Sociocultural context, attitudes, and policy influence characterize bilingual education across urban and borderland settings, with community language norms, choice of instruction, and political dimensions shaping program adoption and efficacy [4], [5], [7], [12], [17].

• Measurement, assessment, and learning-strategy analysis foreground bilingual development, highlighting degree-of-bilingualism metrics, wh-question development, error analysis, and strategy indicators across multiple studies [8], [11], [15], [16], [18].

• Curriculum design and teacher preparation in language education, including ESL pedagogy, language-of-instruction decisions, and elementary-language programs, illustrate how instructional materials and teacher education shape bilingual outcomes [5], [7], [12], [14].