In independent special schools, most of which cater for children with social, emotional and behavioural difficulties, the boy-girl ratio is 3:1, and in special schools as a whole it is 2:1.
"The smallest discrepancy is in the proportion of males and females in the area of profound learning difficulties (55 per cent male, 45 per cent female) and hearing difficulties (59 per cent male, 41 per cent female)," she writes in a journal published by Moray House Institute of Education.
"Similar patterns are evident when comparing . . . girls and boys with recorded special educational needs placed in mainstream primary and secondary schools."
Professor Riddell acknowledges that physiological factors help to explain why boys are categorised as having sensory, physical or profound learning difficulties. Other researchers have referred to males' susceptibility to "germs, genes and trauma". They are, for example, more vulnerable in the womb, and more likely to suffer anoxia (oxygen starvation) and other complications at birth.
But she points out that the gender imbalance is particularly pronounced in those areas where professionals are most likely to make subjective value judgments. "This lends weight to the argument that social judgments and cultural expectations play a significant part in determining who gets labelled as having special educational needs."
Furthermore, statistics reveal how gender interacts with social class in the identification, she says. "Working-class boys are much more likely to be identified as having problems regarded as socially unacceptable such as emotional and behavioural difficulties and moderate learning difficulties.
"In relatively non-stigmatised categories, such as specific learning difficulties, middle-class boys predominate. Dyslexia, largely due to the efforts of voluntary organisations, is seen as a problem meriting sympathy, support and additional resources rather than school exclusion.
"The attachment of the label of special education needs, then, may be advantageous in terms of providing additional support, or disadvantageous by raising the possibility of sanctions or school exclusion."
A key question for Professor Riddell is whether boys gain or lose from their greater likelihood of being identified as having special needs or being placed in special schools. There is no straightforward answer, she says.
Resources are skewed towards boys through their over-representation in special schools, which are much more expensive to run than mainstream schools, and they also receive more learning support in ordinary classes.
On the other hand, Scottish Office statistics indicate that boys with special needs tend to leave school early - in 1993 52 per cent of leavers with special educational needs were under 16. Boys in special schools also tend to lack role models as more than 90 per cent of teachers and 80 per cent of headteachers in Scottish special schools are women.
"Some writers have maintained that the large numbers of working-class boys identified as having learningemotionalbehavioural difficulties should be seen as an attempt to marginalise this group and justify their exclusion from the labour market in which structural employment is endemic," Professor Riddell says. "Afro-Caribbean boys, in particular, are said to be pathologised through this labelling process."
However, it was also true that because girls are less likely to "act out" in the classroom, their difficulties might remain undiagnosed and invisible.
"It is evident that moves to treat everybody the same might have negative consequences for both girls and boys," she says. "Identifying more girls as having emotionalbehavioural difficulties in line with the number of boys so labelled would clearly be counter-productive, given the poor life chances of such pupils. A better solution might be to seek a way of reducing the number of boys excluded from mainstream schools.
In the case of specific learning difficulties dyslexia . . . there might be a case for searching more carefully for girls with such problems. The preponderance of boys identified as having dyslexia is likely to reflect not only boys' greater physiological vulnerability but also social expectations that boys should perform well, coupled with a willingness to devote additional resources to counteract failure . . . The important question to ask seems to be: 'Whose interests do particular labels serve?'" Knitting progress unsatisfactory: Gender and special issues in education, edited by Gwynedd Lloyd, is published by Moray House Institute of Education, Holyrood Road, Edinburgh EH8 8AQ, price Pounds 12.50