The directorate of examination has issued show cause notice to teachers from eight districts in the state, for erroneous evaluation of plus-two answer sheets, this year.
The action comes after the results for plus-two examinations re-evaluation were published recently.
A senior official of the examination department said, in several cases, there was a whopping difference in the marks awarded by the original examiner and that awarded during re-evaluation of the answer sheets of scores of students in 8 districts, including Theni.
The teachers had been issued show cause notice seeking explanation for the differences in the marks of answer sheets evaluated by them.
Action would be initiated if explanation given by them was unsatisfactory and they could be permanently debarred from evaluation work, he added.
Chief examiners, assistant examiners and micro examiners had also been asked to offer explanation in this regard.
The officials found a gap of 75 percent between marks awarded during original evaluation and what the students got after re-evaluation.
The teachers either did not total the marks properly or left out some answer sheets without evaluating them by mistake.
It is normal when the teachers skip one or two pages while totalling, but the mistakes committed are grave in nature apparently, the official said.
Last year, the difference in some answer sheets was 25 percent, but this year it is 75 percent, which is unacceptable by any scale, he added.