Researchers said the findings highlighted the long-term academic risks associated with children being distracted or not paying attention.
The investigation, carried out by academics at Bristol and Nottingham universities, covered more than 11,000 children. Parents and teachers were asked about pupils’ behaviour at age 7, including inattention, hyperactivity or defiance problems. The results were then compared with the students' GCSE scores at age 16.
The study found that, after taking into account other factors, such as parental education and social class, for every one-point increase in inattention symptoms at age 7 there was a two- to three-point reduction in GCSE scores and a 6-7 per cent increased likelihood of not achieving a minimum level of five good GCSE grades, including maths and English, at age 16.
"Across the full range of scores at a population level, each one-point increase in inattention at age 7 years is associated with worse academic outcomes at age 16," the study concludes. "The findings highlight long-term academic risk associated with ADHD, particularly inattentive symptoms."
Kapil Sayal, professor of child and adolescent psychiatry at the University of Nottingham, who led the research, said: “Teachers and parents should be aware of the long-term academic impact of behaviours such as inattention and distractibility. The impact applies across the whole spectrum of scores at the population level and is not just confined to those scoring above a cut-off or at the extreme end.”
Teaching teenagers time-management and organisation skills, minimising distraction and helping them to prioritise their school work and revision, were ways that parents and teachers could help, Professor Sayal added.
The study, which was funded by the Economic and Social Research Council, is published in the Journal of the American Academy of Child and Adolescent Psychiatry.