system or process under copyright. Perhaps you can patent it but the fact that you've shown your method to teachers means you may have missed the boat on a utility patent. Even if you haven't, you're facing an uphill climb (you must prove it's novel and nonobvious), it will be costly (expect to pay north of $5,000 dollars) and it takes time to get a utility patent (two-to-three years) during which time you can't stop copycats.
What would Evelyn do? What do innovators with new methods do to protect their brainstorms if patent protection is unavailable. Perhaps we can take a tip from Evelyn Wood, the woman who popularized the term, "speed reading." Ms. Wood achieved success and dominance in her field by doing four things: (1) getting her system out first -- that is by offering seminars and getting the Reading Dynamics program out soon after publication of her groundbreaking 1959 book; (2) associating the method with her name and the Reading Dynamics trademark -- so consumers sought her out rather than competitors; (3) promoting her method on TV and with celebrities; and (4) securing copyright protection for her materials, and trademark protection for her services and products.
Is the expression of the app considered a different idea? The term "app" refers to a specialized program that accomplishes some task. There may be two copyrightable aspects to an app: its content, for example the dictionary within a dictionary app; and the programming or coding -- the internal architecture that enables a user to access and manipulate the content. You would have a claim against an app if the content within was expressed in a substantially similar manner to your content. For example, if many sections of your writing were lifted verbatim or near-verbatim. You may have a claim if they are similar but not near-verbatim but that depends on the content and whether it is protectable (see above).