Emma Smith of Cardiff University will tell the BERA conference that boys from low-income backgrounds are no more likely to under-achieve than boys or girls from other social groups.
"Many of the pupils labelled in the media as under-achieving are actually low-achieving, she says. Pupils from working-class backgrounds may score lower in national tests at 14 but she argues that this can be put down to a range of factors including previous attainment and motivation.
The research was based on the results of more than 2,000 Year 9 pupils from 12 schools in the South Wales valleys.
Girls from working-class backgrounds were more likely to perform below their potential than their male counterparts. They were also less likely to achieve higher-than-expected results.
But pupils of higher ability - even those in the top sets at school - were also at risk of underachievement and would be "unlikely" to be identified as such by teachers.
The research also found that a pupil's test results at key stage 2 and his or her performance in tests designed to measure mental ability were the best predictors of performance at 14, followed by school attendance.
Copies of "Could do better? An investigation into underachievement at key stage 3" by Emma Smith can be obtained by emailing SmithE@Cardiff.ac.uk