(a) Services performed as a student nurse in the employ of a hospital or a nurses' training school are excepted from employment, if the student nurse is enrolled and regularly attending classes in a nurses' training school and such nurses' training school is chartered or approved pursuant to State law.

(b) Services performed before 1966 as an intern (as distinguished from a resident doctor), in the employ of a hospital are excepted from employment, if the intern has completed a 4 years' course in a medical school chartered or approved pursuant to State law.