Synthesizing research on metacognition and intersecting it with studies on L2 writing, Ivan Chongputs forward a conceptual framework of metacognition and metacognitive knowledge that is employed as an analytical lens to examine primary students' writing proficiencies. The exploration takes into account three facets of metacognitive knowledge namely person knowledge, task knowledge, and strategic knowledge. Based on data garnered from interviews, open-ended questionnaire, and think-aloud sessions with students, the book analyzes the three types of metacognitive knowledge - theorized as a system - of senior primary students with high, average, and low writing proficiencies. Discussion of the findings offers an expanded understanding of the factors that potentially affect students' writing proficiencies, which will inform the teaching of primary and secondary L2 writing teachers to be more learner-centered.