This study aims to investigate the influence of bilingual instruction on the development of language awareness among students. It examines the differences in language awareness between monolingual and bilingual students. The empirical investigation is a two-year longitudinal study that collected data at four measurement points, integrating both qualitative and quantitative methods in a triangulation approach. The study was conducted at three secondary schools in Hesse with a bilingual German-English program in grades 7 and 8. Data collection was carried out using questionnaires, a language awareness test, and a cognitive ability test. The data were analyzed and interpreted using statistical methods such as significance tests and qualitative content analyses.