Poorer children are twice as likely to start school with behaviour problems, new research has suggested.
More than a third (35%) of the poorest three-year-old boys displayed behaviour problems, compared with one in six (15%) of those living in richer households.
The research, by Elizabeth Washbrook of Bristol University, analysed the responses of parents to a Strengths and Difficulties Questionnaire (SDQ) to compare the behaviour of children aged three to seven.
The SDQ asks thousands of parents to rate their child's behaviour in terms of hyperactivity and inattention, conduct problems, emotional symptoms, and peer problems.
The findings show that the proportion of three-year-old boys from the poorest fifth of homes showing clinical level symptoms of behaviour problems was double that of three-year-olds from the higher four fifths of homes, in terms of income.
By the age of seven, a fifth (22%) of the poorest boys still suffered from behaviour problems, compared to one in 10 (10%) of those from richer homes.
Amongst girls the rates, were lower, but nearly three in 10 (29%) of the poorest girls exhibited symptoms of behaviour problems, which dropped to a fifth (20%) at age seven.
The research suggests that the gap in behaviour has widened over the last 10 years.
Girls from low income families who were born in the early 1990s were twice as likely to display behavioural problems than their peers at age seven.
Those born around the millennium were three and a half times as likely to show such symptoms at age seven.