Understand mathematical concepts towards the subject matter can have an effect on increasing student learning outcomes. Efforts that can be made to embody it in learning mathematics by applying the model CORE. CORE through the stages of Connecting-Organizing-Reflecting-Extending students were given room to argue as well as build knowledge in understanding the concept of the subject matter by using the tools in the form of Student Activity Sheets simplify understanding of students against the material.The type of research conducted research experiments. The population of this research grade VII SMP Negeri 1 Nan Sabaris, Padang Pariaman as many as 5 classes. Selected samples of research grade VII.4 as class experiments as much as 26 students and Class VII.1 class as control as many as 32 students.The data of this research is the result of learning math students from the final test.In this research, hypothesis testing using the technique of anava one direction. From the calculation obtained results that tcount > ttable with tcount = version 2.84 and ttable = 1.67 with real α = 0.05 level, therefore the hypothesis rejected. Summed up the results of the study of mathematics students who apply using the model CORE of the Learning Activity Sheets Students are better than on the results of learning math students who applied regular learning in grade VII SMP Negeri 1 Nan Sabaris District Padang Pariaman.From the results of the study authors recommend that teachers of mathematics to apply the model CORE Activity Sheet using students to meninggkatkan the results of the learning of students in learning mathematics. Keywords: CORE, learning outcomes, student activity sheets