I have always believed that in a persuasive or argumentative essay it is not rooted in what you know as opposed to what you can prove. Meeting the evidential burden set forth by the task is extremely important in an argumentative essay. I think that the first task is to assess the validity of your evidence and ensure that what you are presenting is consistent with context. In determining this validity, the next step is to develop a thesis statement, what it is you are going to prove through your essay. In terms of your topic, what does the evidence you have say about learner- centeredness? Once this has been clearly determined, finding three central points to prove your thesis will be critical and the writing of it is contingent on how your evidence illuminates these points.
The argumentative or persuasive essay must contain a thesis that makes a claim. That is, the first paragraph/main point of the essay is to state the claim you are trying to prove.
The main body of your essay (which can be any length, but three paragraphs is a good standard unless your instructor requires a different length) is then used to offer supporting points, explanations and evidence to prove the claim you made in your introductory paragraph.
The concluding paragraph then restates what you have proven, much like the closing argument in a trial.