(1) Except as provided in subsection (2) of this section, no person shall be employed to teach in any public, private, denominational, or parochial school in this state who does not hold a valid Nebraska certificate or permit issued by the Commissioner of Education legalizing him or her to teach the grade or subjects to which elected.

(2) Any person who holds a valid certificate or permit to teach issued by another state may be employed as a substitute teacher in any public, private, denominational, or parochial school in this state for not more than ten working days if he or she begins the application process, on the first employment day, for a Nebraska substitute teacher's certificate and the issuance of such certificate is pending.

(3) Public, private, denominational, or parochial schools in the state may employ persons who do not hold a valid Nebraska teaching certificate or permit issued by the Commissioner of Education to serve as aides to a teacher or teachers. Such teacher aides may not assume any teaching responsibilities. A teacher aide may be assigned duties which are nonteaching in nature if the employing school has assured itself that the aide has been specifically prepared for such duties, including the handling of emergency situations which might arise in the course of his or her work.