JUDGMENT

SINGH, J. :— This appeal is directed against the judgment and order of a Division Bench of the High Court of Andhra Pradesh setting aside the order of a learned single Judge, dismissing the appellants writ petition made under Art. 226 of the Constitution.

2. The appellants are members of the Andhra Pradesh Engineering Subordinate Service as supervisors in Category 1 of the Engineering Branch. The Engineering Branch Category 1 includes officers, namely, Supervisors, Overseers, Head Draftmen, Civil Draftmen, Artists Draftmen, Tracers, Blueprint Operators and Building Mistries. Supervisors are recruited by direct recruitment as well as by promotion from amongst the Overseers. The cadre of supervisors include degree holders in engineering and diploma or licence holders. Both perform the same duties and functions in the engineering branch. Promotion to the post of Assistant Engineer, the next higher post is made from amongst the post of supervisors, in accordance with the Andhra Pradesh Engineering Service Rules 1967. Graduate overseers are given preference in the ratio of promotion to the post of Assistant Engineer inasmuch as the quota of promotion is four to one from amongst the graduate supervisiors and non-graduate supervisors. In addition to the disparity in the matter of promotion, graduate supervisors and non-graduate supervisors are granted different pay. On recruitment to the service of supervisors a graduate supervisor is granted higher starting salary than non-graduate supervisors. Subsequently, a lower pay scale was prescribed for the non-graduate supervisors. Aggrieved the non-graduate supervisors filed two writ petitions in the High Court of Andhra Pradesh under Art. 226 of the Constitution challenging validity of discrimination in prescribing two different scales of pay. The appellants contended that diploma-holder supervisors were entitled to the same scale of pay as prescribed for the graduate supervisors on the principle of equal pay for equal work as they constituted the same service and performed the same duties and functions as those performed by graduate supervisors. The State Government contested their case on the pleading that graduate supervisors and diploma supervisors always remained separate and they were never fused into one service. The two class of employees discharged the same functions and carried out similar duties, but the State was justified in prescribing different pay scales for historical reasons, and also on the basis of difference in the educational qualifications. Plea of discrimination against non-graduate supervisors was denied. A learned single Judge of the High Court Justice O. Chinnappa Reddy (as he then was) by his judgment and order dated February 25, 1974 held that the State practised invidious discrimination without there being valid justification between the two categories of supervisors graduates and non-graduates. The learned Judge allowed both the writ petitions and issued mandamus to the State Government to accord the same scale of pay to the non-graduate supervisors as prescribed for the graduate supervisors under the Government Order dated June 13, 1969. On appeals preferred by the State of Andhra Pradesh a Division Bench of the High Court set aside the judgment of the learned single Judge and dismissed the writ petitions on the finding that the State practised to discrimination and the appellants were not entitled to relief on the principle of equal pay for equal work. Hence this appeal by special leave.

3. This is the second round of litigation by the Diploma-holder Supervisors. Earlier they had challenged the grant of higher quota of promotion for graduate Supervisors on the ground that when graduate and non-graduate Supervisors, belong to the same cadre, and are eligible for promotion, then giving preferential treatment to graduates amount to denial of equal opportunity to the non-graduate Supervisors. This Court in Mohd. Shujat Ali v. Union of India, (1975) 1 S