The law thus covers any file you have created on your computer and either saved to disk or printed. A work does not have to be published to be covered by copyright. Nor does the work have to be registered with the U.S. Copyright Office. The catch is that if the work is not registered and an infringement occurs, you are only eligible to recover actual damages. If the work is registered at the time of an infringement, you may be awarded statutory damages instead and recover all attorney fees, which can be substantial.
Statutory damages can be a much greater amount.
Works of any significance that may be compelling to others probably should be registered. For example, your students may be entitled to copyright protection for assignments, papers, and other works turned in to you, depending upon the nature of the material. Copyright ownership may be assigned to someone else, as is often the case with manuscripts submitted for publication. Most colleges and universities have intellectual property policies that address these issues, and in most cases professors are allowed to keep the copyrights. Work that is supported by grants from external funding agencies may provide a tricky variation on this theme.