Abstract
This paper focuses on the effects of direct focused written feedback and direct unfocused written feedback on preposition acquisition in high school students' writing. Preposition acquisition can be difficult for second language learners, so it is important to improve students' acquisition in this area. At the same time, the effects of different forms of feedback vary for different levels of students. This study aims to answer three questions: (1) What is the effect of direct focused feedback on high school students' acquisition of prepositions in English writing? (2) What is the effect of direct unfocused feedback on high school students' acquisition of English writing prepositions? (3) What is the most effective feedback for students of different levels (high, medium, and low subgroups)? This experimental study included a pre-test, two tasks, an immediate post-test, a delayed post-test, and an interview. In this process, meta-linguistic variables were also added to the direct focused feedback and direct unfocused feedback types because some previous studies claim that meta-linguistic explanations have no positive effect on acquisition.