The purposes of this study are to investigate how mathematics achievement can be explained in terms of motivational beliefs (intrinsic goal orientation, extrinsic goal orientation, task value, control and learning beliefs, self efficacy for learning and performance and test anxiety), self-regulated learning components (cognitive strategy use and self-regulation), gender and school types and to determine the differences between two gender (girls and boys) and two school types (public schools and private schools) with respect to the variables above in the subject domain of mathematics. The study was conducted in Istanbul and Ankara, two largest cities of Turkey, with 577 seventh-grade students (274 boys, 303 girls) from nine private and public schools. Motivated Strategies for Learning Questionnaire (MSLQ) and Mathematics Achievement Test (MAT) were used. By using Linear Stepwise Regression and MANOVA, respectively, the results indicated that (1) The combined effect of three predictor variables (school type, self-efficacy and intrinsic goal orientation) on students&rsquo / mathematics achievement was significant. Boys&rsquo / mathematics achievement at public schools was significantly affected by extrinsic goal orientation and cognitive strategy use whereas self-efficacy and intrinsic goal orientation were two predictors for boys at private schools. Girls&rsquo / mathematics achievement both at public and private schools was significantly affected by self-efficacy. (2) There was no statistically significant mean difference between girls and boys with respect to task value, self-efficacy and test anxiety. Also, there was no statistically significant mean difference between public schools and private schools with respect to extrinsic goal orientation, task value, self efficacy and self-regulation.