The scheme, intended to persuade more 16-19s to stay on in full-time education either in school or at college, will leave some youngsters outwith its scope. John Swinney, the former SNP leader, wanted the Executive to change the rules.
But in a parliamentary written answer, Allan Wilson, Deputy Lifelong Learning Minister, told Mr Swinney: "Although extending eligibility would benefit a small group of students this year, it would immediately create further costs and anomalies in the staged roll-out which would be difficult to justify.
"It is inevitable, when any new scheme is rolled out, that some will fall on the wrong side of the qualifying date. While I recognise their disappointment, we considered it fairer to adhere to eligibility criteria for which there is a rational basis in terms of the policy objectives of this scheme."
The Executive is gradually extending EMAs, with support of pound;16 million this year increasing to pound;42 million by 2008.
It is estimated the scheme will eventually benefit 40,000 young people.
Depending on income, those accepted for allowances will be entitled to weekly payments of pound;10, pound;20 and pound;30.
Strict regulations set out in learning agreements contract those taking part to continue in full-time education with 100 per cent attendance. The allowance is only paid in term time.