B. SUBHASHAN REDDY, C.J. :--The question in this batch of writ petitions and connected writ appeal is whether the doctrine of legitimate expectation, which is a judge-made law, can be invoked to assail the changed Government policy relating to improvement examination as promulgated in G.O. Ms. No. 142, School Education Department, dated 12-9-2001.

2. We may have to go to the genesis of the said Government Order, which is impugned in this batch of writ petitions. Henceforth, the said G.O. Ms. No. 142, dated 12-9-2001 will be referred to as the impugned G.O.

3. The Government of Tamil Nadu evolved a scheme enabling the students to re-appear in the Higher Secondary Examination for improvement called 'improvement examination'. That was introduced for the first time, by issuance of G.O. Ms. No. 1457, Education Department, dated 7-10-1989. It is needless to mention that the said Scheme has been evolved in exercise of the State's executive power under Article 162 of Indian Constitution. The Scheme for the Award of Higher Secondary Course Certificate was introduced in 1978 and the first batch of Higher Secondary candidates appeared for the examination in March 1980. Before the issuance of G.O. Ms. No. 1475, only such of the candidates, who failed in the subjects, were permitted to write further examinations in the failed subjects. But by the said G.O. Ms. No. 1475, the candidates, who have even passed in the subjects were allowed to improve their performance by appearing in the examinations further. The conditions for availment of the said improvement scheme have been specified and they are as follws :

i) Candidates can apply and appear for improvement of their performance in one or more subjects within the Group already offered two times only.

ii) Candidates should be allowed to improve only the group of subjects already appeared and passed.

iii) The examination fee for reappearance shall be Rs. 40/- for each subject.

iv) The Higherst marks secured in each subject in the different sittings shall be taken as qualifying marks.

v) No separate 'Consolidated pass certificate' shall be issued to the candidate. For every appearance, a separate certificate (mark statement) shall be issued as is done for SSLC.

vi) The facility of improvement of marks is open to be availed of by candidates who have appeared for the higher secondary examination since its introduction in Tamil Nadu in March/April, 1980.

vii) such candidate, who apply for improvement, should be allowed to write the examination only under the pattern and syllabi in vogue at the time of their reappearance.

4. The above condition in clause (i) has been relaxed further by issuance of G.O. Ms. No. 181, Education Department, dated 19-2-1993 to all other courses excepting professional courses. So far as the professional courses, the impugned scheme was restricted for two times only. But the choice of appearing in one or more subjects already passed was not distrubed. It is pertinent to mention that the Scheme of Improvement has not been confined only for the students who have passed after G.O. Ms. No. 1457 but had been made applicable retrospectively for all such students of Higher Secondary course, who have passed the examination even conducted from March 1980 onwards. This is to emphasise that the Scheme was made applicable to all the students of Higher Secondary Examination appeared from March 1980 onwards, subject, of course, restricting the number of attempts to two in the improvement examination. The academic year starts from June of each year to the month of April of the succeeding year. To be precise, for these cases, the academic year started in June 2001 and would end in April 2002. The main examination would be in March 2002 and the supplementary examination has already been held in September 2001. For September 2001 examinations, notification was issued and published in newspapers dated 24-6-2001 inviting applications for Higher Secondary Examinations. It contains three colum