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
Apple has marked the 10th anniversary since the first iPhone went on sale.
A man who walked six miles a day to and from work was left astonished after a stranger presented him with a car bought from donations.
Police have charged Pope Francis's top financial adviser - Australia's most senior Vatican clergyman - with historical sex offences.