Children who do not get into a grammar school will find themselves in "lower ability peer groups", which, in turn, "affects their chances of succeeding at school".
Professor Simon Burgess from the University of Bristol, who led the research, also said the inequality could be explained by the calibre of teaching in both types of schools.
Selective schooling systems sort pupils based on their ability and schools with high ability pupils are more likely to attract and retain high quality teaching staff.
This puts pupils who miss out on a grammar school place at an immediate disadvantage.
In addition they will be part of lower ability peer groups, which also affects their chances of succeeding at school.
More top news
Celebrities including Chris Evans and Joanna Lumley are expected to attend the event marking 50 years since the broadcaster went on air
Staging a 'feast in a cemetery' is an important date in the calendar of one of Europe’s last surviving ethnic folk cultures, the Setos.
What was the reaction online to the first presidential debate that saw Clinton and Trump go head-to-head?