The aim of the conducted research was to examine the extent to which sociodemographic variables, students' personality traits and dimensions of parental behaviour contribute to prediction of general school achievement and school achievement in certain groups of subjects (linguistic, mathematical, humanities and art). There were 153 high school students in the area of Crikvenica and Rijeka that participated in the research, of which 51 were boys and 102 were girls. To examine the predictive power of sociodemographic variables, students' personality traits and parental relationship dimensions to predict school achievement, a series of hierarchical regression analyzes were conducted. Sociodemographic data was included in the first step, personality traits were included in the second step and dimensions of parental behaviour were added in the third step of the analysis. The obtained results indicate that conscientiousness, openness to experience and age are the most significant positive predictors of general school achievement, but also school achievement in certain groups of subjects. The most significant negative predictor of general school achievement, but also school achievement in certain groups of subjects is parental rejection. The paper discusses predictive effects of presented predictors in the context of existing models and the results certainly contribute to the prediction and overall understanding of school achievement of high school students.