The aim of this study was to investigate the application of behaviourist theory in classroom instructions, focusing on effectiveness and challenges. Data were collected from public school teachers in Sargodha, Pakistan, using a mixed-method approach. The data analysis highlighted that the majority of teachers are familiar with Classical and Operant Conditioning principles. The findings indicated that behaviourist strategies such as token economies, behaviour contracts, and reinforcement are effective in managing classroom behaviour, improving student engagement and enhancing student academic performance. However, challenges such as inadequate teacher training, extrinsic and intrinsic motivation balancing, and consistency in implementation were noted. Recommendations include improved teacher training, clear behavioural expectations, and increased administrative support to optimize the use of behaviourist strategies in classroom instructions.