Although research generally attests to the beneficial role of transformational leadership (TL) for school effectiveness, little empirical work has distinguished individual- from group-focused dimensions of TL and analysed their relationships with target variables at the individual and group level of followers simultaneously. Using a dual effects model of TL, the present study aims to fill this gap. It examines the dimensional structure of principals' TL behaviours and their prognostic value for teachers' self- and group-referential efficacy beliefs. Additionally, contextual dependencies of leadership effects are considered through the moderating role of a principal's span of control. Based on questionnaire data of 1,702 teachers in 118 Swiss schools, doubly latent ML-SEMs specify moderated dual effects of TL on both teacher and school levels of analysis. Results convey empirically separable latent sub-dimensions of TL (individual-/group-focused), which (a) characterise systematic differences in the leadership behaviours of the investigated principals and (b) substantially predict variations in the mean-levels of both teacher and collective efficacy between their respective schools. TL-collective efficacy relations are stronger in close leadership situations (low span of control) than in distant ones.