Section 12-304. Application of chapter

This chapter shall be applicable to:
    a.  All  municipal  agencies  and  to  the public employees and public
  employee organizations thereof;
    b. any agency or public employer, and the public employees and  public
  employee  organizations  thereof,  which  have been made subject to this
  chapter by state law;
    c. any other public employer, and to the public employees  and  public
  employee organizations thereof, upon the election by the public employer
  or the head thereof by executive order of the chief executive officer to
  make  this  chapter  applicable,  subject  to  approval  by  the  mayor,
  provided, however, that any such election by the New York city board  of
  education  shall not include any teacher as defined in section 13-501 of
  the administrative code or any employee who works in  that  capacity  or
  any para-professional employees with teaching functions; and
    d.  any  public employer, and the public employees and public employee
  organizations thereof, to whom the provisions of this chapter  are  made
  applicable pursuant to paragraph four of subdivision c of section 12-309
  of this chapter.