Since 'education' is in concurrent list, centre alone cannot initiate any steps unilaterally. But, we may persuade through High Court, Supreme Court and all India Professional bodies like MCI, AICTE etc. to advise all the states to follow weighted average marks to determine the eligibility for admission to professional courses.
It needs a little explanation.
No. of students who scored centum in a particular subject, multiplied by 100.
No. students who scored 99 marks in the same subject, multiplied by 99.
And so on.
Finally, these are to be added and average found.
Then weighted average for each board examination (State, Matriculation, CBSE, ICSE etc.) separately is to be found. Finally, the percentile score by taking the median under each stream to be arrived.
This will be a fair and just mechanism, so that no student is discriminated because of the choice of his syllabus or educational system.