This study assumes that the best way of teaching mathematics is a well suited tutoring based on each child’s interests, attitudes, intellectual capabilities and the level of understandings of the prerequisites. But any public school system cannot afford this, while it can instead provide various other merits like social involvements etc. that students need. And we believe that under the current mass education system. parental guide is a possible solution to prevent the learning deficiencies in mathematics learning. We studied which contents of the elementary school geometry is the most important to learn the next coming subjects. Those were found to be: 1. Basic Figure; 1) line segment / line 2) perpendicular / parallel line 3) angle 2. Plane Figure; 1) triangle 2) square 3) circle 4) the circumference & the area of the plane figure 3. Transformation; 1) Congruence 2) Symmetry 4. Cubic Figure Secondly we found the kids are mostly confused and get difficulties to understand for the followings. 1. The similar sphere (like the line segment / line) cause the confusion. 2. When the form and position of between a textbook and an authentic situation, it can cause the visual errors. 3. There are many misconceptions of the inclusive relation of the triangle the square. 4. There are many misconceptions of the circumference and area by the visual errors. 5. The transformation (congruence, line symmetry & point symmetry) showed misconceptions of the homologous sides & angle. 6. Many cases make it hard to distinguish between plane figure and cubic figure. Our work is to give parents ideas to help kids geometrical understandings through errands, family games, travels, home handicrafts etc. that might occur often at home but not so usual at school or at any artificial classes.