§ 683-a. Presentation of grievance. Every public school teacher shall have the right to present his grievance to his employer in accordance with the provisions of this article, free from interference, coercion, restraint, discrimination or reprisal, and the grievance procedure established under this article shall provide the right to be represented at all stages thereof and the representative shall be designated by the public school teacher at the time he presents his grievance or at a subsequent date.