The teaching of paragraph writing at the high school level refers to the basic manners of academic writing, in which a paragraph is expected to meet the three criteria: unity, cohesion, and coherence. However, many high school students find these criteria difficult to utilize in their writing. To support such students, the author developed thinking tools to make the criteria more accessible to them. By practicing writing with the thinking tools, the students have learned to organize paragraphs that meet the criteria.