Implicit theories of intelligence play a role in teacher's actions. Adaptive instruction in and out of the classroom is important to optimize learning processes, especially in the case of at-risk students. This study explored to what extent implicit theories of intelligence play a role in the actions of educational professionals around at-risk students. Forty-four teachers and 57 support professionals participated in this research. Data were analyzed separately for teachers and support professionals. Thirty-four percent of the actions of the teacher can be explained by implicit theories. However, in denominational schools this is 61%. Structural equation modeling showed mediation effects of multiple belief factors in the actions of support professionals. Implicit theory of intelligence predicts the belief in IQ testing, which precedes the belief in consequential validity of tests (i.e., link to actions according to test outcomes). These results indicate a strong influence of implicit theories of intelligence in educational practice.