It's not "principle" it's "principal."
From Dictionary.com: "A principal is “a chief or head, particularly of a school.” Principal can also be used as an adjective meaning “first or highest in rank, importance, or value,” as in The principal objective of this article is to teach you the difference between two words."
"A principle, on the other hand, is “rule of action or conduct” or “a fundamental doctrine or tenet.” Principle is often associated with and used as a synonym for moral, meaning “of, relating to, or concerned with the principles or rules of right conduct or the distinction between right and wrong.”
Keep up, ChicKie.