The work with four-year-olds helped to narrow the skills gap between boys from higher and lower socio-economic backgrounds, according to researchers from University College London's Centre for Research and Analysis of Migration (CReAM).
The study found that all children benefit from early schooling, but the average effects are weaker compared to those for disadvantaged boys - who carried the impact on cognitive and non-cognitive skills into the final year of primary school.
The report, Early School Exposure, Test Scores and Noncognitive Outcomes, includes data analysis of more than 400,000 children born in 2000/2001 attending state schools in England.
It found providing an additional term (four months) of early schooling for disadvantaged boys increased their test scores in language and numeracy at age five by up to 20 per cent.
Their personal, social and emotional development at the same age improved by eight per cent, and their language and numeracy skills at age seven by around 10 per cent.
However, for boys from high socio-economic backgrounds, the results for many of these effects were close to zero.
The study points at why boys from low socio-economic backgrounds benefit more strongly from early schooling and concludes they may experience lower quality childcare when not enrolled in early childhood education.
Researchers also looked at variations in school entry rules for the reception year and cases of summer-born children in some local authorities who were deferred entry by one or two terms.
The results showed on average all children given an additional term of early schooling increased test scores in language and numeracy by up to 10 per cent, and age seven language and numeracy skills by around two per cent.
While the effects on cognitive skills largely disappear by the time children reach 11, the study found there were lasting effects on non-cognitive outcomes.
For children aged five, physical development, creative development and personal, social and emotional development increased by around five per cent for one extra term of early schooling.
Earlier school entry further improved the pupil-teacher relationship and non-cognitive skills such as academic interest and good behaviour at ages seven and 11.
Professor Thomas Cornelissen, CReAM research fellow, said the starting age of formal schooling was the earliest in the UK compared to other countries, but there was little evidence on the optimal starting age.
"Our findings confirm that exposure of four-year-olds to early learning in a school setting fosters a range of important social skills throughout age five, seven and 11.
"The idea behind deferment by one or two terms is to give the youngest children some time to become school-ready," he said, adding: "But it seems that on average, the negative effect of losing one term of reception class outweighs the potentially positive effect of deferment, in particular for boys from disadvantaged family backgrounds."
Commenting on the research, a spokeswoman for the Early Years Alliance said it was important to note how and when the early learning happens.
For example, quality early learning can begin prior to reception, in nurseries, pre-schools or childminding settings, whereas the study featured an earlier start in reception.
The impact can differ, depending on whether the child is experiencing early learning for the first time in school.
"This is particularly important when looking at the impact of deferring school entry for summer-born children, as spending more time in an early years setting should not be seen as 'losing' time in reception class," added the spokeswoman.
She continued: "We know that access to high quality care and education has particular benefits for children who are disadvantaged and that the EYFS [Early Years Foundation Stage], facilitated by practitioners who have a good understanding of how individual children learn, is the means through which we can instil a life-long aptitude for learning."