Ten "toxic" ingredients of modern life are making children harder to teach than 30 years ago, a leading educational consultant has warned.
Sue Palmer spent three years interviewing teachers and academics before identifying a damaging mix of technology, family breakdown and poor diet.
She says these factors explain worsening behaviour and an explosion in numbers of special needs pupils.
Ms Palmer believes parents could help address problems by having regular family meals and taking televisions out of children's bedrooms.
Her research follows the publication of a study of 10,000 pupils earlier this year, which revealed a fall in the number of 11-year-olds able to grasp basic maths and science concepts since 1976.
The number of children being diagnosed with attention deficit hyperactivity disorder (ADHD) has soared. One report last month said that NHS prescriptions for a drug to treat the condition had increased three-fold since 1999.
Ms Palmer, a TES contributor and writer on literacy and behaviour, said:
"Children are easier to distract and more impulsive than a few decades ago.
This causes problems with discipline. It is a significant factor in the problems we have teaching reading and the explosion in special needs."
Her research identified 10 causes of the behaviour shift: access to modern technology, a lack of outdoor play, poor sleep patterns, lack of communication with adults, the testing culture in schools, pressure from advertisers, changes in family structure, poor advice to parents contributing to worsening manners, sleep deprivation and diet.
Her findings, due to be presented at the Education Show in Birmingham yesterday, will be published in Toxic Childhood in May.
However, Mick Brookes, general secretary of the National Association of Head Teachers, disputed that children were now harder to teach, based on his observations from 30 years teaching in primaries. He said: "Perhaps older children know their rights better and this may erode the authority of the teacher in some instances, but I don't see a specific trend. A few decades ago, badly behaved children were just badly behaved children. Now we can identify all manner of psychological conditions to explain their behaviour."
Last month The TES Scotland told how a researcher at Oxford university had estimated that up to a quarter of pupils had some form of learning impediment caused by the lack of vital nutrients in their food. Alex Richardson, who is at the forefront of research on putting omega-3 fatty acid back into children's diets, carried out a controlled study in the Durham area. In the study 117 under-achieving children with motor difficulties who were given fish oil supplements made "stunning"
improvements in reading and spelling. Most benefits were in attention span and better behaviour from pupils with ADHD.
Another study, released this week, cast doubt on the link between television and behaviour. Researchers at Texas Tech university tracked two groups of 2,500 children's viewing habits over two-years from the age of five, and found that their exposure to television had no bearing on their risk of contracting ADHD later. "It may be that exhausted parents of very active and inattentive children resort to using the television as a 'babysitter' more commonly than do parents of less active and more attentive children," it said.
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