Disparity of academic achievement in students seems to be bigger as the students are promoted in recent years. Since the students don’ t acquire basic academic skills of mathematics sufficiently in junior high school, they find difficulty to understand mathematics for the lower students. Then the lack of understanding makes the disparity of academic achievement in students. This paper reports a project to progress in basic academic skills of mathematics for the lower students. This project is realized refresher instruction of mathematics that students have studied before. Teachers implement from development of teaching materials to planning and direction for this project consistently. A regularly scheduled test and questionnaire research demonstrate that the project is effective for progressing in basic mathematical skills.