One in 10 children might have a "working memory" impairment that causes them to do less well than expected at school, research suggests.
The researchers say teaching strategies can be adjusted
A Durham University team identified the problem in 10% of more than 3,000 schoolchildren, across all ages.
They say teachers rarely identify it, tending to label pupils as being unmotivated daydreamers.
Working memory involves such things as remembering verbal instructions, new names or telephone numbers.
The researchers say that if the finding of 10% of children having the problem held true for all children, then almost 500,000 in primary education alone would be affected.
COMMON CLASSROOM CHARACTERISTICS
Low abilities in literacy and numeracy
Frequent failure to complete learning activities
Frequent failure to remember instructions
Normal social integration with other children, but
Very reserved in groups, rarely volunteer information
The researchers believe that early assessment - which they say can be done reliably from the age of four - would enable schools to adopt new teaching methods.
As things stand, they say misdiagnosis commonly results in children being labelled as inattentive or lacking in motivation.
Their diagnostic tools have been piloted in 35 schools across the UK and translated into 10 foreign languages.
Lead researcher Dr Tracy Alloway, from Durham's school of education, said: "Working memory is a bit like a mental jotting pad, and how good this is in someone will either ease their path to learning or seriously prevent them from learning.
"From the various large-scale studies we have done, we believe the only way children with poor working memory can go on to achieving academic success is by teaching them how to learn despite their smaller capacity to store information mentally."
A teacher's hunch that something is wrong can be followed up by getting the child to do a computerised assessment.
The team's recommendations for coping with the problem include repetition of instructions, talking in simple, short sentences and breaking down tasks into smaller chunks.