Background: Previous studies have shown that subjective well-being and adaptability are linked to adaptive educational outcomes, including higher achievement and lower anxiety. It is not presently clear, however, how school-related subjective well-being and adaptability are related, or predict behavioural outcomes such as student conduct. Aim: The aim of the present study was to test a bidirectional model of school-related subjective well-being and adaptability, and how they relate to achievement and behavioural conduct. Method: Data were collected from 539 Year 12 students over four waves. Achievement and behavioural conduct were measured in the first wave of data collection (T[subscript 1]), school-related subjective well-being and adaptability at the second and third waves (T[subscript 2] and T[subscript 3]), and achievement and behavioural conduct again in the fourth wave of data collection (T[subscript 4]). Results: A structural equation model showed that T[subscript 2] school-related subjective well-being predicted higher T[subscript 3] adaptability, but not vice versa. T[subscript 3] school-related subjective well-being predicted greater T[subscript 4] achievement and positive behavioural conduct, and T[subscript 3] adaptability predicted greater T[subscript 4] positive behavioural conduct. Conclusion: School-related subjective well-being promotes adaptability, achievement, and positive behavioural conduct, and adaptability is also related to positive behavioural conduct. Attempts to foster well-being and adaptability could show educational gains for students.