The purpose of this study was to examine the effect of three types of praise activities on school adjustment of sixth graders. We assume that there are three types of praises; Verbal reinforcement, Encouragement, and Social acknowledgment. The study is based on pretest-posttest experimental design. The subjects of this study were 55 six- grade students who enrolled to two classes of an elementary school located in Busan. One class (26 students) was an experimental group and the other class(29 students) was a control group. Three types of praise activities were applied to the experimental group for 11 weeks. The activities were composed of classroom activities for understanding of the concept of praise, online activities, praise card activities for practicing three types of praises. School Adjustment Scale developed by Lee Young-Sun(1997) was administrated to all the subjects as the pre and post-test. To verify the effects of the experiment, ANCOVA was conducted. The treatment group showed a statistically significant increase in school adjustment, but the control group that received a neutral intervention did not.