Writing in English with confidence is a matter of great concern for non-native speakers. Since writing fluently requires a multi-dimensional mastery of language skills, students always regard it as an open question. This book investigates writing skills which seem to be the least favored and most problematic skills to acquire in foreign language acquisition. The book is a valuable reference for teachers and instructors of English all over the world who are eager to develop their students' writing fluency. The book covers the development of major writing skills such as organization of ideas, self-expression, meaning construction, coherence, and writing mechanics. In addition, the book introduces a solution by implementing a new-born theory, Differentiated Instruction, that had a great impact on the educational arena. Moreover, the book is full of new ideas and concepts for enhancing High School Students' writing fluency.