Social anxiety (SA) is a common experience for many children when faced with social situations. This study presents the application of a play-based school program in social skills training (SST) for children aged between 9 and 12. The experimental group consisted of 87 students from disruptive classrooms. From this group we further analyzed a subgroup of children with high SA (n= 34). A reference group of 25 students, belonging to a non-disruptive classroom from the same school served as a comparison group for the program’s social validation. SA was assessed with the “Social Interaction Questionnaire for Children” (SAQ-CIII), giving an overall score of social anxiety and specific ratings in each of six dimensions. Results at post-intervention and at 6-month follow-up showed an improvement in the experimental group and, in particular, the high SA subgroup, with large effect sizes. In addition, this subgroup of high SA decreased their social anxiety at post-intervention to the same level as the reference group in four dimensions of the SAQ-CIII and on the overall social anxiety score of this questionnaire. These results provide initial support for the effectiveness of SST with children for decreasing SA.