Copyright protects the expression of an idea, but not the idea itself. This means that if you have an idea for a great teaching plan, it will only become protected by copyright once it is recorded in writing (or otherwise), but it would not be protected by copyright if it was simply in your head and you told someone else about it orally.
In the case of a literary, dramatic, musical or artistic work, or other written work, the work also has to be original, which (broadly speaking) means that its author spent independent effort to create it and did not copy it from other works.
Note that you cannot stop someone who has independently, and without copying your work, created the same or a substantially similar work to yours. In this situation, both those works would be protected by copyright in their own right and each copyright owner could prevent others from copying his/her protected work.
Information contained within these pages is intended as general guidance only. This information is not intended to be, and should not be, relied upon as legal advice.