Teach the beginning. Write a prompt on the board, such as "More schools are moving toward student uniforms. Is this good or bad?" Ask the student if he has strong feelings about school uniforms. If he is for sure he is against the idea, tell him to craft his introduction and thesis from that point of view. Tell him to jot down the three main reasons that he is against school uniforms. Coach the student to write something like: School uniforms are a bad idea because they tend to be ugly, are expensive and don't allow me to express my individuality.
Teach the students to nail down the middle. Coach the students to use the three main points from their introduction as the main points for the three middle paragraphs of his essay. For instance, the first paragraph will explain why the student feels the uniforms are ugly. Have him write about some uniforms that he has seen students wear, what schools they were from, what colors they were. If needed to fill the paragraph out, ask the student to add what his parents, friends or relatives have said about school uniforms. Do the same thing for the other two key points, and the body of the essay will be written.
Close with a strong ending. Bolstered by his thesis and body, the student will be armed to end with a strong summary and conclusion. Teach students the concept of 1. Tell the readers what you are going to tell them (intro). 2. Then you tell them (body). 3. Finally, you tell them what you told them (conclusion). Teach them to write a summary that reinforces their intro: "In closing, expensive and ugly school uniforms really don't solve any problems, and they don't allow a student a chance be whom he wants to be."
Repeat and reinforce. Allow the students to get comfortable with the notion of writing prompts. Allow them some class warm-up periods to fine-tune their extended response essays by writing a second and a third draft. Advise them to start with an outline and/or a story web or story map to make the piece more focused. Also, give students extended response assignments of varying lengths: 10 minutes, 15 minutes, 20 minutes and 30 minutes.