This paper discusses the constructs of students' metacognitive competencies and its effect on mastery of learning strategies and enhancing learning outcomes in the context of high school in Shanghai, China, where Learning to Learn curriculum has been implemented for years. 780 students from three types of typical high schools in Shanghai participated in a questionnaire survey. Result of a structural equation model shows that metacognitive knowledge, planning, monitoring, and evaluation constitute students' metacognitive competencies which effectively predict mastery of learning strategies and their student learning outcomes. Pedagogies for metacognitive teaching for effectively implementing the Learning to learn curriculum are proposed.