Measuring School Climate among Japanese Students—Development of the Japan School Climate Inventory (JaSC)

School climate is a significant determinant of students’ behavioral problems and academic achievement. In this study, we developed the Japan School Climate Inventory (JaSC) to see whether it measures school climate properly. To do so, we investigated whether or not the measurement with JaSC varies across sub-groups of varying grade and of gender and examined the relationship between the perception of school climate and the psychological and behavioral traits at individual levels in a sample of Japanese elementary and junior high school students (n = 1399; grade 4–9). The results showed that the measurement was consistent, since single-factor structures, factor loadings and thresholds of the items were found not to vary across sub-groups of the participants. The participants’ perception of school climate was associated positively with quality of life, especially in school (β = 0.152, p < 0.001) and associated negatively with involvement in ijime (bullying) as “victim” and “bully/victim” (β = −0.098, p = 0.001; β = −0.188, p = 0.001, respectively) and peer relationship problems (β = −0.107, p = 0.025). JaSC was found to measure school climate consistently among varying populations of Japanese students, with satisfactory validity.