(2) Preference shall be given for appointment under clause (1) or sub clause (a) of Clause (iii) of sub clause 1 (a) Firstly to persons with First or Second class P.G. Degree: (b) Secondly to persons with a third class Post Graduate Degree with not less than five years of service as Post Graduate Assistants or Selection Grade Assistants in the Andhra Pradesh Educational Subordinate Service or as a Head Master of a Zilla Parishad High School or as a Post Graduate Assistant in a School under the management of a Zilla Parishad or a Municipality; (c) Thirdly to person with a third class Post Graduate Degree with less than five years of service as a Post Graduate Assistant or a Selection Grade Assistant in the Andhra Pradesh Educational Subordinate Service or as a Head Master of a High School or Post Graduate Assistant in a school under the management of a Zilla Parishad or of Municipality. . . . . . . ".