Relationships between students' grade-level, epistemic beliefs, metacognition, and science achievement were investigated separately for low and high-achieving schools. A total of 587 students in low achieving schools and 600 students in high achieving schools from fifth, sixth, and eighth grades constituted the study sample. Exploratory and confirmatory factor analyses identified two factors for both epistemic beliefs and metacognition measures. Results of the structural equation modelling showed that path coefficients from grade-level to quick/fixed learning, regulation of cognition, and knowledge of cognition were all negative and significant in both low and high achieving schools' models. In addition, path coefficients from certain/simple knowledge to regulation of cognition and knowledge of cognition were all positive and significant in both models. Moreover, quick/fixed learning and knowledge of cognition were significant contributors to students' science achievement, regardless of students' school type. However, several school-type differences regarding path coefficients of epistemic beliefs factors with other variables were observed. Interestingly, the effect size of the science achievement model was greater in low achieving schools compared to the same model in high achieving schools. Implications of these findings about how to improve students' epistemic beliefs, metacognition, and science achievement both in low and high achieving schools are discussed.