Changes in students' self-reported psychological flexibility scores and teacher-rated behavioral difficulties during a year-long, teacher-delivered social-emotional learning curriculum based on acceptance and commitment therapy.

This study examined longitudinal changes and social validity during implementation of a culturally adapted, teacher-delivered social-emotional learning curriculum grounded in acceptance and commitment therapy (ACT) and applied behavior analysis (ABA) in Czech public primary schools. Participants were 448 children in Grades 2-5 from 23 classrooms across 10 schools. The year-long program was implemented as part of routine classroom practice, with assessments at baseline, midyear, and post-implementation. Students completed a shortened Czech adaptation of the Children's Psychological Flexibility Questionnaire (CPFQ), and teachers completed the Strengths and Difficulties Questionnaire (SDQ) and rated program social validity. Psychometric evaluation indicated substantial limitations in the CPFQ, including suboptimal factorial fit and low reliability of some subscales; the Present Moment subscale was excluded from longitudinal analyses, and changes in the remaining subscale scores were treated as exploratory. Linear mixed-effects models showed small increases in Acceptance and Defusion subscale scores, no clear linear change in Self-as-Context or Values scores, and a small decrease in Committed Action scores. Teacher-rated SDQ outcomes showed consistent changes in a favorable direction, including teacher-perceived reductions in emotional symptoms, conduct problems, hyperactivity, peer problems, and total difficulties, alongside increased prosocial behavior. Because the same teachers delivered the curriculum and rated children's behavior, with no parent, independent, or blinded assessments, these findings reflect teacher-perceived change. Teachers generally evaluated the program favorably while identifying time demands as the main constraint on implementation. Overall, the findings document favorable changes during implementation, particularly in teacher-rated functioning, while highlighting limitations in the measurement of psychological flexibility and the need for controlled evaluation.