This study was conducted to analyze the structural relationship between teachers’ competencies, democratic school climate, learning organization culture, and teacher efficacy, and multi-group analysis was conducted to compare changes before and after COVID-19. In order to achieve the purpose of the study, the competencies of middle school teacher was classified into four, which are teaching competency, student guidance competency, community competency, and ICT utilization competency, by referring to the previous studies and the data of the 4th and 5th years of the Busan Education Longitudinal Study. The results of the study are as follows: first, the school climate had a direct impact on community competency in both 2019 and 2020, and was found to have a particularly significant impact on the learning organizational culture. Learning organizational culture had an effect on teacher efficacy, teaching competency, and community competency, and teacher efficacy had a strong influence on all variables of teacher competencies. The democratic school climate directly affected only the community competency among the four competencies in 2019, but in 2020, it had a significant influence on strengthening the teaching competency and student guidance competency in addition to the community competency. Second, as a result of examining the mediating effect using phantom variables, it was confirmed that only the path in which the school climate affects the teaching competency through the learning organizational culture and teacher efficacy as a medium has a significant partial mediating effect in both 2019 and 2020. Third, as a result of multi-group analysis before and after COVID-19, a significant difference was found in the path that the democratic school climate had on the learning organizational culture, and it was found that the learning organizational culture in 2020 after COVID-19 is more affected than the previous year by the school climate. Based on the above results, policy implications are presented to help strengthen the teachers’ competencies.