Pupil's scholastic achievement in learning social studies show the difference under the influence of various factors. This is an experimental research taking the socio-economic status as one of these factors. Children's socio-economic status are classified into D_x (white-collar workers), D_y (official laborers or wage workers), D_z (daily-workers), and A (farmers). The experiment has been conducted at the fourth grade classes, divided into experimental and control groups according to the pupil's socio-economic status. After the children studied on a same unit (transportation) in the classes, their learning effect were evaluated by test, as to the degree of knowledge and understanding. The result indicated at the score of various groups appeared different along the order of D_x, D_y, D_z, A. However changing the content of units containing the knowledge chiefly related to living-experiences, these differences became decreased, specially in learning effect of D_z group. The fact indicates that the difference of children's achievement attributing to socio-economic status is caused from the character of teaching materials, but from the nature lies in status. Therefore it can be said that children's scholastic aptitude is subject to be equalized and democratized by means of changing curriculum. It is neccessary to accommodate children to curriculum on one hand, but to adapt curriculum to children's abilities is needed on the other hand. This is the basis of the psychological approach to the curriculum reconstruction.