Objectives The purpose of this study is to examine the aspects of teachers’ feedback based on high school students’ persuasive writings and their assessment. In particular, it attempts to check the aspects of teachers’ feedback on how teachers give their feedback to students depending on writing level by categorizing types of feedback, which lead to look for effective feedback. Methods For this study, 30 of the third graders in high school wrote the persuasive writings about animal experiment and the papers randomly were distributed into 5 teachers. The papers were divided into level of writing(advanced, intermediate, beginner) and gender. Teachers’ feedback on 150 writings were categorized and frequency and correlation were analyzed throughout the categorization. It is analyzed that there are any differences in the contents of feedback depending on students’ writing level. Results Teachers involved mostly concentrated on the factor of the vocabulary(953 feedback) of all the feedback(2862 feedback), while the least feedback is the factor of critical opinion(2 feedback). In detail, feedback on structure of writing, metacognition occurs most often in the advanced levels of performance, feedback on detail of contents in the intermediate levels of performance and feedback on sentence, comprehension of subject in the beginner levels of performance. Conclusions As a result, it is shown that most of the teachers still tend to give students feedback on form of writing like vocabulary correction and revision and grammar like word spacing, punctuation marks for accuracy in expression. In addtion, teachers’ feedback depending on writing level show obvious differences in the target with the result that writing feedback is classified in this study. The study has significant implications for constructive feedback on writing.