The study, by academics at the universities of Bath, Bristol and London University’s Institute of Education, analysed the pay of more than 2,500 people born in the 22-year period between 1961 and 1983.
They found that in areas with a selective education there was a bigger gap between the wages of the highest and lowest paid individuals than when compared to areas which operated a comprehensive system.
On average, the hourly wage difference between the top 10 per cent and bottom 10 per cent of earners born in selective schooling areas was £16.41 between 2009 and 2012.
However, in areas which have a comprehensive system but are otherwise similar, the equivalent earnings gap was £12.33.
This is despite average earnings in both types of area being almost identical – £8.59 in selective areas and £8.61 in non-selective.
The researchers analysed information gathered by Understanding Society, a study that is following the lives of people in 40,000 UK households.
Even after allowing for factors such as gender, ethnicity, parents’ education level and occupational class, they found that 18 per cent of the income gap between the highest and lowest earners could be explained by the school system.
The researchers also revealed that the highest earners from grammar school areas are significantly better off – by £1.31 per hour on average – than top earners born in similar comprehensive authorities.
High-earning men appear to gain most from selective school systems.
The study states: “Cohorts of students growing up in areas with a selective education system experience greater earnings inequality once in the labour market.
“If higher earnings inequality is coupled with socially graded access to grammar schools then it seems likely that selective systems will also reinforce inequalities across generations.”
The lowest earners from areas with selective schools receive significantly less than their non-selective counterparts, with the gap at the bottom of the income scale being most evident among women. The lowest-paid women from selective areas earn £0.87 less per hour than women from non-selective authorities.
One explanation for this may be that a disproportionate number of girls were assigned to secondary modern schools in the past, the researchers say.
Professor Simon Burgess from the University of Bristol, who led the research team, said that the inequality caused by selective schooling systems could be explained by the quality of teaching: “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.”