(20) State means a State, a political subdivision of a State, or any agency or instrumentality of a State. For this purpose, the District of Columbia is treated as a State. In addition, for purposes of determining whether an individual is an employee performing services for a public school, an Indian tribal government is treated as a State, as provided under section 7871(a)(6)(B). See also section 1450(b) of the Small Business Job Protection Act of 1996 (110 Stat. 1755, 1814) for special rules treating certain contracts purchased in a plan year beginning before January 1, 1995, that include contributions by an Indian tribal government as section 403(b) contracts, whether or not those contributions are for employees performing services for a public school.