Basic Psychological Need Satisfaction and Frustration in the Ecology of School Principals: A Multitrait-Multimethod and Nomological-Network Examination of the BPNSFS

School leaders face intensifying demands, creating a leadership crisis. We apply Self-Determination Theory (SDT) to examine how leaders’ basic psychological needs operate under constrained autonomy—formal authority amid persistent external controls. Using survey data from 1,950 Australian school leaders, we offer a substantive–methodological reflection that (a) extends validation of the Basic Psychological Need Satisfaction and Frustration Scale (BPNSFS) with novel methods and (b) demonstrates SDT’s relevance to demanding leadership roles. We validate the BPNSFS two-facet structure—three needs (autonomy, competence, relatedness) crossed with two valences (satisfaction, frustration)—across two waves via a 3×2 multitrait–multimethod (MTMM) design with time as method. We then link this structure to a nomological network of 64 workplace variables spanning job demands, resources, well-being, and burnout. Our substantive–methodological synergy supports four propositions: • Satisfaction and frustration are separable and differentially predict well-being and ill-being; • Active need thwarting and frustration, especially of autonomy, relates more strongly to ill-being than merely insufficient satisfaction; • Demands map more strongly to frustration, while resources align more strongly with satisfaction, consistent with the Job Demands–Resources (JD-R) model and SDT’s dual process model; • Content-specific patterns emerge—autonomy relates to voice and justice, competence to efficacy, and relatedness to collegial support. Across bivariate and multivariate (orthogonal-contrast) tests, autonomy frustration predicts burnout and intent to leave, whereas autonomy satisfaction predicts professional commitment and well-being—evidence of a constrained-autonomy paradox in which leaders have formal authority but limited practical discretion—extending SDT through methodological synergy in service of theoretical development.