The purpose of the study was to explore school culture in radically different schools due to school achievement. The particular objectives of this study were to investigate: (1) the teachers' perceptions of school culture (2) the teachers' perceptions of principal behaviors, and additionally (3) to determine the relationship between principals' behaviors and perception of school culture by teachers. This study employed a comparative-descriptive research design and took place in A - Middle School, representing a high-performing school, and B -Middle School, representing a low-performing school. These two middle schools were both located in capital city of Poland and were selected based on their position in Warsaw Middle Schools Ranking. The "School Culture Survey" (Gruenert & Valentine, 1998) was used to obtain data about school culture factors. To determine the teachers' perceptions of principal's behaviors, "The Organizational Climate Description Questionnaire - Middle Level" (OCDQ-ML, Hoy et al., 1996) was used. Statistical comparisons of collaborative school culture indicated that the compared schools differ significantly in four school culture dimensions. In school A there is a culture focused on individual achievements, the competition more than cooperation, unlike the situation in B-middle school, in which collaborative school culture is strong and visible. According to principal behaviors, significant differences between compared schools were also identified. Namely, more supportive principal behaviors were typical for school B (low school performing), while restrictive principal behaviors were more common in school A (high-performing). Results indicated that principal behaviors and collaborative school culture were associated with each other.