When used as a job description, it is a common noun and is not capitalized.

Do you capitalize vice principal in a sentence?

Job titles and positions

Capitalize an individual's title when it directly follows their name, separated by a comma. Lowercase a title when it appears on its own, separated from the individual's name. The dean expects results by 2014; Tom Harris was appointed vice-principal of advancement in 2010.

Do military ranks get capitalized?

Capitalize a military rank when used as a formal title before an individual's name. ... If one is used before a name in a subsequent reference, do not capitalize or abbreviate it.