Interventions are not always implemented with fidelity in education thereby confining their effectiveness. Socially valid interventions that match the needs and demands of teachers are implemented with more fidelity. This design study aims to elucidate which factors enhance or impede the social validity of an intervention aimed at promoting the social participation of students with disabilities. A social validity assessment via interviews was conducted with 17 kindergarten teachers. The results show that teachers evaluated the intervention on all three dimensions of social validity: goals, procedures, and (expected) effect. Teachers were predominantly positive about the intervention, though, five intervention aspects were considered challenging and need alteration. This study demonstrates that social validity assessment can be a valuable tool in refining interventions.