The term “employment” does not include services performed in the employ of any organization in any calendar quarter beginning after June 30, 1956, and during any part of which such organization is registered, or there is in effect a final order of the Subversive Activities Control Board requiring such organization to register, under the Internal Security Act of 1950 (50 U.S.C. 781 et seq.), as amended, as a Communist-action organization, a Communist-front organization, or a Communist-infiltrated organization.