This study investigates the effects of formative assessment, specifically neutral assessment and encouraging assessment, on students' learning performance in the short- and long-term. Through the use of quasi-natural experiments, Propensity Score Matching, and Instrumental Variable methods, the study finds a consistent and significantly positive effect of neutral assessment and encouraging assessment on students' learning. It also reveals an interesting effect: encouraging assessment helps to inspire students to cope with difficult tasks in the long term, while neutral assessment only improves the performance of short-term, loose, and relatively easy tasks. This suggests that encouraging teaching intervention helps to shape students' long-term aptitude for handling difficult tasks, while neutral assessment only boosts short-term, loose, and relatively easy work performance. The findings of this study suggest that formative assessment, and particularly encouraging assessment, can be an effective tool for improving student learning in the short- and long-term.