The development of students is often marked by the success of achieving student achievement in school. The achievement is often used as one of the benchmarks of the success and performance of a school. However, it is possible that on the other hand the development of students is also influenced by family and environmental factors. This study aims to find empirically factors such as Peer Group, Parental Involvement and Classroom Climate in forming Student Achievement. Research method with the correlational approach. The sample of the study were 148 students. Data collecting technique with Likert Scale questionnaire ranges from 1 to 5. Construct validity of each questionnaire with Principle component axis through Varimax Rotation with the eigen value of 0.600. The results showed that: first, there was positive influence of Peer Group (X1), Parental Involvement (X2) and Classroom Climate (X3) both individually and collectively to Student Achievement with Ry123 of 0.710 with variance determination of 0.504. That is, the contribution of Peer Group (X1), Parental Involvement (X2) and Classroom Climate (X3) together in form Student Achievement students of 50.4% while the rest of which is 49.6% formed by at least 1 (one) other variables Based on the residual sum of squares ratio of 2482.448 with sum of squares regression of 2520.579. While Fregression generated at 48.737 is very significant at α <0.01. The decisive main role of forming Student Achievement is Classroom Climate (X3) with t of 5.182 is very significant at α <0.01. The second determinant role of forming Student Achievement is Peer Group (X1) with t equal to 4,047 is very significant at α <0.01. Secondly, there is a difference in Student Achievement if the differentiated level of education with F of 3.991 is significant at α <0.05. Apparently fourth-grade elementary school better achievement than class student 5 and 6 with average equal to 30.5294 and standard deviation equal to 4.86207 significantly at α <0,05. The implication of the research is the need to develop new policies in education governance through the realization of an educational model that creates Transformational Classroom Climate and learning that focuses on Peer Group through Cooperative Learning in order to increase the capacity and potential of students to be maximal in order to maximize Student Achievement.