The plans, spelt out last week by Department for Education and Employment officials, stunned college managers and school sixth-form heads.
The senior registrar of one South London college said: "This will be the first birthday lottery since the United States' government Vietnam draft and probably about as popular."
The pound;100 million scheme gives pound;40 a week to encourage young people who stay on post-16. But there is too little cash for everyone in the pilot areas to receive help. Government officials are to hand responsibility for the pilots to local partnerships.
The pilots have already been attacked for raiding access cash to fund pilots in the 12 pilot areas, taking money from the most needy 16 to 19-year-olds and leaving adults with little or no support.
David Gibson, chief executive of the Association of Colleges, told MPs this week that the allowances should not be restricted to teenagers. He was responding to a question from Don Foster MP, Liberal Democrat education spokesperson. Mr Foster said: "The one thing that is missing is a pilot for post-16 students. They have a variety of other sources of funding but they are messy."