As used in this chapter:

1. (1) "Employer" means a school district which receives funding from the State from the annual appropriation to the Department of Education for Aid to School Districts--Employer Contributions in the annual general appropriations act.

2. (2) "Employee" means a person employed full time by a public school district who is:

   1. (a) certified and teaching in the classroom;
   2. (b) assisting a certified classroom teacher;
   3. (c) a professional specialist having direct contact with students;
   4. (d) an academic subject, or specialty area coordinator or director working in a school or school district;
   5. (e) a principal, vocational center director, assistant principal or vocational center assistant director, district assistant, county or area superintendent.
3. (3) "Participant" means an employee who participates in the optional retirement program provided by this chapter.