Children who find it difficult to focus when they are six years old earn less as adults, research suggests.
A study found six-year-olds who have their 'head in the clouds' take home less each year when they reach their thirties.
When their lack of focus was scored from zero-to-three, just a one point decrease led to the boys earning $1,271.49 (£1,007) less a year.
Inattentive girls suffered a $924.25 (£732) salary cut, according to the research by the University of Montréal.
Aggressive boys who bully, bite or kick pay the consequences in later life, earning on average $699.83 (£554) less a year. However, the same was not true for girls.
Researchers worry poor concentration at school may affect a youngster's academic performance, which then impacts their career path.
And violent boys may mix with 'the wrong crowd', which also sets back their school achievements.
Children who struggle to focus in reception earn less as adults, research suggests (stock)
The research was led by Dr Sylvana Côté, a professor in the school of public health.
'Our study shows that childhood inattention is associated with a wide range of long-term adverse outcomes, including lower earnings over the course of a career,' the researchers wrote in the journal JAMA Psychiatry.
Poor attention spans, hyperactivity and aggression in childhood have been linked to everything from unemployment to financial woes in later life.
This has 'implications for society', with such individuals being more likely to suffer from mental health conditions and to claim benefits, the researchers add.
However, childhood behaviours may be 'modifiable' and are arguably easier to change than IQ or family background.
To uncover how our childhood attention span impacts later salary, the researchers analysed data from the Quebec Longitudinal Study of Kindergarten Children.
The study asked primary school teachers to rate the behaviour of 2,850 five-to-six year olds.
Inattention was defined as 'having one's head in the clouds', lacking concentration and being easily distracted.
The teachers also noted any hyperactivity or physical aggression, such as kicking and biting.
These were rated on a three-point scale, with zero indicating never and three often.
In the first study of its kind, the same children's government tax returns were analysed when they reached 33-to-35.
Attention Deficit Hyperactivity Disorder (ADHD) is a behavioural condition defined by inattentiveness, hyperactivity and impulsiveness.
It affects around five per cent of children in the US. Some 3.6 per cent of boys and 0.85 per cent of girls suffer in the UK.
Symptoms typically appear at an early age and become more noticeable as a child grows. These can also include:
Constant fidgeting Poor concentration Excessive movement or talking Acting without thinking Little or no sense of danger Careless
