It shows that all other things being equal, being in a grammar will add almost 16 GCSE points to a pupil's attainment at 16.
But the report also suggests there is a heavy price to be paid for the grammar pupils' success.
Thousands of children who fail the 11-plus are arriving at secondary modern with poor self-esteem and little self-confidence.
It comments: "Teachers in secondary schools say many pupils arrive with a sense of failure."
The Government-commissioned report was published as anti-grammar school campaigners in England this week gave up the fight to end selection in Kent.
They blamed Education Secretary David Blunkett for making their mission impossible and accused him of hiding behind parents over the issue of ballots on the future of grammar schools.
At a Labour party conference fringe meeting this week they claimed that recent rule changes in England would leave them gagged, if their pro-grammar opponents decide to stay silent during campaigns.
And Becy Matthews, a parent from Kent, said: "If David Blunkett is against the 11-plus, then he should stop hiding behind this inadequate piece of legislation and behind people like me."
Children in Northern Ireland have been examined at the age of 11 since 1947, but parents, teachers and educationists are fiercely divided on whether the tests put children under too much pressure.
The report claims that many parents are so desperate for their children to pass the test that they are paying up to pound;15 an hour for extra lessons, even though they often cannot afford it.
The research, by Professor Tony Gallagher of Queen's University, Belfast, and the University of Ulster's Professor Alan Smith, also found that the test has a "backwash effect" on the key stage 2 curriculum, with emphasis being put on preparing for it at the expense of a "broad and balanced experience".
Employers, however, claimed their views of individuals are not affected by whether they had passed the 11-plus. Subsequent achievements and qualifications are more important to them.
The report, entitled "The effects of the selective system of secondary education in Northern Ireland", is posted at www.deni.gov.uk