The re-grading will be applied to grades from the students' senior secondary education years because only the grades from these levels will account for the 30 per cent of weighting in this year's university-admission criteria. Last year, the grades carried only 10 per cent of the weighting.

Starting from the 2005 academic year, students' grades from Grade 10 to Grade 12 are graded into one of eight categories, but before the new system was introduced there were only five categories. The new grades are rated 0, 1, 1.5, 2 and so on to 4. Previously the grades were simply sorted into categories 0 to 4.

"Without the re-grading, the students who completed Grade 12 prior to the 2005 academic year would be at a disadvantage [in the chance to enter their favoured universities]," Chaturon said yesterday.

However, he said the re-grading would be made for students whose secondary schools still kept their raw scores only. About 75 per cent of some 40 schools which had already contacted the Education Ministry on re-grading said they had kept the students' raw scores. Chaturon said each school that planned to re-grade their students would establish a committee to ensure that the re-grading was conducted transparently.

"Schools must submit the students' new grades to the Office of Basic Education Commission before the end of this month," he said. In a related development, Office of Higher Education Commission secretary-general Pavich Thongroj said the scores of the Ordinary National Educational Test (O-Net) and Advanced National Educational Test (A-Net) would be announced in the afternoon of April 30 through websites and a call centre.

"Just dial (02) 576-5555 if you want to check the scores via phone," he added. This year, the O-Net and A-Net scores will be used as main university-admission criteria.