Purpose: In light of limited sustainability of past collaborative-learning-centered initiatives over time, the purpose of this paper is to explore the determinants considered by both teachers and principals to influence the sustainability of a collective-learning-from-success (CLS) initiative in 12 urban elementary schools. Design/methodology/approach: Using qualitative methodology, data were collected via face-to-face interviews with 37 teachers and eight principals. Analysis involved identifying common themes, contrasting patterns, and elucidating differences among participants' voices. Findings: In total, six major determinants were identified as influencing the sustainability of the CLS initiative: superintendent's role, principal's role, need for a structured learning setting, burden added to teachers' workload, overuse of theory and underuse of practice, and congruence with school agenda. Originality/value: As researchers and practitioners explore ways to sustain collaborative learning in schools, it is important to further evaluate whether learning communities can be developed and sustained when staff members are encouraged to collectively analyze their successful practices.