As used in this article: “Agency” means any department, institution, authority, instrumentality, board or other administrative agency of the government of the Commonwealth of Virginia and any transportation district created pursuant to the Transportation District Act of 1964 (§ 33.2-1900 et seq.) of Title 33.2 and Chapter 630 of the 1964 Acts of Assembly. “Employee” means any officer, employee or agent of any agency, or any person acting on behalf of an agency in an official capacity, temporarily or permanently in the service of the Commonwealth, or any transportation district, whether with or without compensation. “School boards” as defined in § 22.1-1 are not state agencies nor are employees of school boards state employees. “Transportation district” shall be limited to any transportation district or districts which have entered into an agreement in which the Northern Virginia Transportation District is a party with any firm or corporation as an agent to provide passenger rail services for such district or districts while such firm or corporation is performing in accordance with such agreement.