The Independent Schools Council expects public school pupils to be three times as likely to achieve the top grade as their counterparts in state schools.
Only a handful of universities across the country are actually asking for the new A* in their offers to school leavers, however, including Cambridge, University College London and Imperial College London.
Independent Schools Council's chief executive David Lyscom said: "It looks as if we will get a disproportionate number of A* grades. Our pupils will perform very well at A* because of the way they are taught.
"Not being taught to a particular exam but teaching around the exam makes our pupils better at doing exams. It also means they are better suited for the demands of A*."
But even if students pass with high marks, many could still miss out after the Government admitted the number who will be unable to get place at university was set to rise, despite 10,000 extra places being made available.
Higher Education Minister David Willetts said: "There has been a surge in applications so sadly there are going to be a significant number of young people who apply for university and don't get a place. Getting to university has always been a competitive process but it is going to be very tough this year, I don't disguise that.
"Last year there were 160,000 young people who applied and didn't get a place. It could be a greater number this year."
Professor David Green, the vice-chancellor of Worcester University said he believed that the number of available places would be slightly fewer this year.
He blamed controls introduced by the former Labour Government which meant that universities faced a fine of 3,700 for each student they admitted above their allocated total.
Prof Green said: "People are going to do absolutely all in their power to avoid over-recruiting which of course inevitably will mean that they will undershoot and that the system as a whole will undershoot because everybody will try to under-recruit."
He expected around 200,000 students would fail to get places, against 125,000 two years ago.