This research investigated the influence of the classroom environment on students’ achievement, specifically focusing on English classes in an Islamic boarding school, SMP Islam Ummulqura Indonesia, Bireuen, Aceh. This research also went in-depth to identify the most influential factors within the classroom environment that affected students’ achievement in learning English. Employing a quantitative research approach and a correlation research design, the study utilized purposive sampling to select the representative population. The sample comprised 108 second-grade students, from whom 105 completed questionnaires were collected and analysed. Data analysis was performed using Multiple Linear Regression analysis via SPSS Software. The findings indicated that the social factor was the most influential aspect of the classroom environment. This suggested that positive social engagement within the classroom significantly contributed to successful academic achievement in English learning. The study concluded that all examined factors—psychological, social, and physical—simultaneously and significantly impacted students’ achievement. Thus, teachers were encouraged to build strong relationships, support students' mental health, and the school also needed to create an engaging classroom layout to optimize the learning process.