Researchers have claimed that parents appear to be planning autumn births to ensure that their offspring are among the oldest in their year at school, the Daily Mail reports.
Studies have revealed that youngsters born at the beginning of the academic year in September are more likely to perform better in exams than those who are "young for their year" or born in July and August.
The study has also suggested that poorer families, whose children are entitled to free school meals, appear not to be making such deliberate calculations.
It has warned that middle-class "conception decisions" are partly to blame for one of the biggest problems facing education - the continuing poor performance of children from working-class homes.
The study of 3 million children, called 'When You Are Born Matters', also revealed that even at 16 after 11 years of schooling, the impact of a pupil's month of birth can be seen in General Certificate of Secondary Education (GCSE) results.
While 60.7 per cent of September-born girls achieve at least five A* to C grades at GCSE, only 55.2 per cent of girls born in August do so.
Of boys born in September, 50.3 per cent achieve at least five C grades, compared with only 44.2 per cent of those born at the end of the school year.
The study, conducted by the Institute for Fiscal Studies, has called for "urgent" action to address the issue, including adjusting pupils' test scores to take account of their age.