(2) Preference shall be given for appointment under clause (i) or sub clause (a) of clause (iii) of sub rule (I)(a): (a) Firstly to persons with first or second class Post Graduate degree; (b) Secondly to persons with a third class Post Graduate degree with not less than five years of service as a Post Graduate Assistant or Selection Grade Assistant in the Andhra Pradesh Educational Subordinate Service or as a Headmaster of a Zila Parishad High School or a Post Graduate Assistant in a school under the management of a Zila Parishad or a Municipality; (c) Thirdly to persons with a third classs Post Graduate degree with less than five years ' service as a Post Graduate Assistant or Selection Grade Assistant in the Andhra Pradesh Educational Subordinate Service or as a Headmaster of a High School or Post Graduate Assistant in a School under the management of a Zila Parishad or a Munici pality. ." 553 The Andhra Pradesh Government decided in 1964 that the Secondary School Education should be of 10 years ' duration instead .