(1) The term “professional employe” shall include those who are certificated as teachers, supervisors, supervising principals, principals, assistant principals, vice-principals, directors of career and technical education, dental hygienists, visiting teachers, home and school visitors, school counselors, child nutrition program specialists, school librarians, school secretaries the selection of whom is on the basis of merit as determined by eligibility lists and school nurses.

(2) The term “substitute” shall mean any individual who has been employed to perform the duties of a regular professional employe during such period of time as the regular professional employe is absent on sabbatical leave or for other legal cause authorized and approved by the board of school directors or to perform the duties of a temporary professional employe who is absent.

(3) The term “temporary professional employe” shall mean any individual who has been employed to perform, for a limited time, the duties of a newly created position or of a regular professional employe whose services have been terminated by death, resignation, suspension or removal.