Purpose: Limited attention to messages transmitted between principals and teachers led to the general question for this study: is principal support of student psychological needs related to functional social conditions within the instructional core? Therefore, the purpose of this paper is to define principal support of student psychological needs and explain its leadership function through the lens of conversation theory. Without much empirical evidence to draw from, a theoretical argument for how principal support of student psychological needs might influence the features of the teaching and learning environment is advanced then tested empirically. Design/methodology/approach: Hypotheses were tested using a non-experimental, correlational research design based on "ex-post facto" data collected from teachers and students in 93 schools in a metropolitan city of the USA. Data were collected in the spring of 2017 from randomly sampled teachers and students in the 93 schools. Usable responses were received from 1,168 teachers, yielding a response rate of 66 percent. A total of 4,523 students received surveys and usable responses were received from 3,301, yielding a response rate of 73 percent. Multi-level modeling was used to analyze the data. Findings: Principal support of student psychological needs was related to school-level differences in faculty trust in students, collective teacher efficacy and student perceived autonomy support. Leadership practices surrounding professional development and instructional coherence had moderately strong, positive relationships with the outcome variables; however, the strength of these relationships diminished when principal support was included in the analysis. Originality/value: The argument in this study proposes that principal-teacher conversations enhance leadership practices and support a vibrant and engaging instructional core when intentional messages build mental representations that enable teachers to understand sources of optimal student growth. Such use of conversation extends the functionality of principal-teacher interactions beyond that of teacher control and toward an ongoing sense-making and learning process.