Purpose: Accounts for failures of merit pay in educational settings were stagnated by the "political obstruction hypothesis," which blamed teacher unions for impeding the merit pay schemes from proper function. It required stronger evidence from both public and private schools to refute this hypothesis. Design/Approach/Methods: Accountability typology was conceptualized to uncover the power relations underpinning merit pay schemes, and teachers' motivational status was described from the perspective of Self-Determination Theory (SDT) to analyze the corresponding consequences. One public school and three private schools were purposefully sampled, and data included principal interviews, teacher interviews, school documents, and relevant policy documents. Findings: Our findings suggested an opposite conclusion to the "political obstruction hypothesis" that the more dependent on market, the more intense the conflict between external accountabilities and the nature of teaching. Thus, we supported the "nature of teaching hypothesis" that merit pay was inapplicable in educational settings due to the inherent contradictions between market accountability and professional accountability. Originality/Value: Policymakers and school administrators had been misled by the neoliberal initiative of borrowing merit pay into educational settings to promote the quality of teaching. Our findings provided strong evidence to refute this hypothesis and to restore the appreciation of professional autonomy.