Medium of instruction (MoI) has turned into a matter of dispute in post-colonial societies for various conditions, such as favoring foreign languages over local or native tongues, enacting monolingual laws in multilingual communities, and creating inconsistencies between education policies and practices. This study aims to give a critical overview of MoI policies and practices from primary to higher secondary levels and their social, economic, and cultural effects in Bangladesh. The study employed a systematic literature review approach as part of secondary research. The study finds Bangla as a medium of instruction (BMI) by de jure and English as a medium of instruction (EMI) by de facto, which results in a remarkable inconsistency between MoI policies and its existing practices in the education sector. The further notable finding suggests that the mismatch between MoI policies and its practices leads to a disparate education structure and, eventually, a stratified society marked by inequalities, social hierarchies, marginalization, and so on. More importantly, the inequalities characterized by MoI practices are twofold: on the one hand, EMI is a source of division and inequalities for the Bangla-medium students, and on the other, BMI acts similarly when it comes to ethnic minority students.