When should I capitalize the word "principal"?

When using the word Principal to describe the head or director of a school, under what situations should one capitalize it, and when should it be lower-cased?

Solution 1:

Principal should be capitalized when used as a title preceding the name of the person but uncapitalized if used as a description following the name. For example,

Let us welcome Principal Bob.

Let us welcome Bob, the principal of the school.

See for example Blue Book of Grammar and Punctuation.

Solution 2:

Tips on the capitalization of the word principal:

• you should capitalize the word principal when it goes before a proper noun, such as "Principal Skinner", or "Mr. Skinner, Principal of Springfield Elementary School".

• you should not capitalize the word principal when the word stands alone without a person's name like "we're sending you to the principal".