The aim of this article is to analyse how professionals in special needs upper secondary schools in Sweden -- assistants, teachers and Special Education Needs Coordinators -- understand and define quality in their daily interactions with students who have intellectual disabilities. Our analysis draws on data collected via a digital questionnaire, including both open-ended and standardised (Likert scale) questions. In this study, written excerpts from open-ended questions comprised the primary empirical data used in the analysis. 129 respondents provided a total of 289 statements concerning their views on quality in professional encounters. In order to explore the semantic content of the written excerpts, the empirical data were analysed using thematic content analysis. Our findings show that perceptions of quality can be categorised differentiated into three typological themes or aspects: individual, relational and contextual. Our findings also show that differences in responses -- both frequency and content -- appear to be associated with the respondents' professional affiliation. Based on these findings, the article suggests the need for an established and shared theoretical basis -- in education and practice -- of what constitutes quality in professional encounters with students who have intellectual disabilities.