This study explores whether there are any differences between the scores of amotivation, extrinsic motivation, and intrinsic motivation of a middle school group and a high school group. It examines the effects of two factors on the difference in the scores of each motivation subtype: whether students receive private education, and when students first start learning English. T-test results indicate higher scores for the middle school group in all the subtypes than for the high school group. Statistical significance was not obtained in support of the effect of private education. The group that started learning English in the third grade of elementary school showed a higher amotivation mean score than the group that started in the first or second grade. Also, amotivation was proven to be a viable variable to group subjects with in addition to extrinsic motivation and intrinsic motivation, supporting the motivation system proposed in Selfdetermination Theory. These results imply that teachers need to understand motivation as a dynamic construct and attempt to promote it through groupspecific approaches in English classrooms.