Based on the discussion in the previous section, it can be seen that the infusion lessons had a positive impact on the students’ thinking. Since these infusion lessons focused on both the development of thinking and the learning of language, it is also valuable to investigate their impact on the students’ writing. This chapter first explores the students’ perceptions of the effects on their writing, based on data obtained from the interviews and post-intervention questionnaires . Then the effects on overall proficiency, accuracy , syntactic complexity and fluency of writing are presented. The analysis of writing was based on the written texts of the 21 students in the infusion class who handed them in both pre- and post-intervention .