The purpose of the present study was to identify and rank factors influencing parents rage in response to the service encounter quality in private primary schools. This research took an applied approach regarding the objective, while in regard to data collection, an exploratory approach (qualitative-quantitative) was used. In the qualitative section, in-depth interviews were used to extract criteria and indices. The statistical population in this part was comprised of 12 experts. After two stages, seven criteria were identified as influencing factors on parents rage. These criteria were “not being accountable (0.725), inappropriate outcome quality (0.85), process inadequacy (0.825), poor quality of interaction (0.75), poor service (0.65), not fulfilling promises (0.775), and inappropriate physical condition (0.35)”. In the quantitative section, grey ARAS ranking technique and three expert votes were utilized. The results of the weighted matrix showed that the strongest criteria for parents rage were inappropriate outcome quality and process inadequacy. Since inadequate quality of outcome is the most common cause of parents rage, its improvement can significantly reduce parents rage.