kieraw is correct in writing that technically, you automatically have a copyright in the work, but registration is generally necessary to enforce it in court. And since the US adopted the Berne Convention (an international agreement on intellectual property), you no longer have to use the little "c" symbol, though Barbarellany is right to say that it does provide a gentle reminder to people. Also, though this is more about the subject line than the actual topic, you cannot copyright an idea. Your copyright applies to the work itself; it is only when another's work bears sufficient similarity to another's work that infringement is shown. Finally, infringement is generally proven by showing the time sequence of the creation of works, their similarities, and is even easier to prove when the alleged copier had access to the original work...so it would seem to me that an unscrupulous tutor would find himself or herself in some degree of peril...