This three-year project uses a cognitive approach to investigate how bilingual education and children’s individual characteristics influence the development of first and second languages (Mandarin and English). The individual characteristics include age, cognitive ability, family background, and language learning experience. Environmental factors can be divided into social and family environment factors, such as cultural factors, low family socioeconomic background, low parental expectations and support, and school factors, such as school district, teaching style, teacher beliefs and expectations, curriculum materials, and peer influence. This project will develop standardized reading tests to measure children’s Chinese and English abilities and a questionnaire to investigate children’s family background and language experience. The second, fourth, and fifth graders from urban and rural elementary schools will participate in the two-year follow-up study. These results will provide scientific evidence for teaching strategies and curriculum design for bilingual education.