One way to make the essay better is to tighten up the writing, removing whatever doesn't need to be there. The introduction can be shortened or altered to get the reader more directly to the actual topic. Many paragraphs can be made more compact, which will leave room to say more.

On the substance, the route to improvement is to make richer, once again, by tightening at the conceptual level. Holmes asked, "does punishment deter?" We still don't know, but restorative justice processes in schools are not only designed to deter, but also to instruct. What punishment instructs in, as you say, is the expectation of punishment and the taste of injustice. So you can put your message more succinctly while only making it stronger.

You can also put the idea in current social context, by looking at the Obama Administration "Dear Colleague" letter on discrimination in school discipline and the predictable pendulum swing away now going on in the DeVos Education Department. This allows you to put something around your policy discussion that doesn't have to end with the comparative doubtfulness of "Love, empathy and forgiveness as opposed to school disciplinary codes may promote optimal social behaviors."