Students do not have access to Turnitin. One reason for this is because of how Turnitin works. To detect plagiarism, Turnitin compares submissions to everything it has in its database. As soon as you submit something to Turnitin, it becomes part of its database, meaning that a second or third draft will come back as heavily plagiarized because of the previous versions submitted.
Another reason why is because we want students to become familiar with all of the ways academic dishonesty can happen, and how to avoid it. Many of these topics are covered in our suite of tutorials.