Boys are far more likely to attend special schools or to be placed in special classes in mainstream schools compared to girls.
Department of Education data shows that in special schools, boys outnumber girls two to one.
In special classes in mainstream schools the differential is even greater, with three boys enrolled for every one girl.
The vast majority of special classes in mainstream schools - 92% - cater for autistic children.
The data has given rise to calls for more research in the area to understand the reasons behind the disparity as well as any potential impact.
"We have a huge lack of evidence here, a lack of research," Selina McCoy, Associate Research Professor at the ESRI and Adjunct Professor at Trinity College, said.
"We definitely need to look at which students are being supported in special classes and how they are experiencing those settings," she added.
Of the 21,315 children enrolled in special classes in mainstream schools, 15,585, or 73%, are boys.
Of the 10,026 children attending special schools, 6,741 are boys.
In these schools too, autism appears to be a significant driver of the gender differential.
Autism advocacy groups suggest later diagnosis of the condition in girls is likely to be a key cause of the gender imbalance.
Adam Harris, the CEO of autism advocacy group AsIAm, said: "Many autistic girls continue to wait longer for diagnosis than boys.
"Autistic boys may be diagnosed at a younger age and when we think about autism classes and special schools, very often children apply for places at the stage of junior infants."
He said the data is "an invitation for us to improve our diagnostic services so that we can identify autistic girls at an earlier stage".
Ms McCoy said: "We don't know whether [the gender imbalance] reflects the timing of diagnosis of some disabilities.
"It may be that girls are being identified later and as a result are missing that entry point into special classes and special school settings, but we need research to understand all of these things."
Imbalance raises questions
While autism used to be regarded as significantly more prevalent in boys, the consensus now is that there is no great disparity.
But the gender imbalance in special education is at odds with this and raises many questions.
Among them whether girls or indeed boys are being placed at a disadvantage.
Are some girls' needs being ignored to their detriment?
On the other hand, are some boys being channeled too readily into a special education pathway that it is almost impossible to get back out of and is one that it likely to have a significant negative impact on their future lives including their job prospects?
However difficult it may be to secure a place in a special class or school, educators say the chances of a child reverting from special education back into mainstream education is harder still.
Research
Ten years ago, the ESRI and Trinity College Dublin conducted a study which looked at the profile of students going into special classes and their experiences in those settings.
Back then, the number of special classes in mainstream schools stood at 942.
Now there are four times that number - 3,742 - and an additional at least 400 are expected to open next year.
With that level of growth, it is not surprising that Ms McCoy, co-author of that study, said the research from 10 years ago is now "very much out of date".
She is concerned that with the massive growth in special classes and with the opening of more special schools, little if anything is known about the outcomes for children taking these pathways.
Ms McCoy said: "[10 years ago] there certainly was evidence that some students were going into special classes who may have been better placed in mainstream and vice versa, so we definitely need to look at who goes into these settings and whether their needs are met.
"We also need to look at whether special classes are operating as a fluid and flexible form of provision, which they are intended to be by policy.
"The research from 10 years ago suggested that once a student went into a special class setting, they remained there, and that is not what the policy intended.
"The intention was that students dip in and out of those settings as and when the need arose, learning needs or socio-emotional needs."
As to whether the gender imbalance might mean that some children, boys or girls, might be losing out, Ms McCoy said "it’s difficult to know" because it is not known how these students are faring compared to their peers in mainstream settings.
"We really need to understand why more boys are going into these settings, and whether that is having a negative impact on them or not," she said.
On girls, she said "maybe they’re missing out on the kind of additional supports they might benefit from in those settings", adding "we need to research this".
Mr Harris blames the historic under-identification of autistic girls upon the fact that initial research "completely overlooked" the female autistic experience.
While there have been significant improvements in the understanding of autism in women and girls, Mr Harris said current levels of understanding mean that girls continue to wait longer for diagnosis compared to boys.
"Many autistic girls present differently to autistic boys," he said.
"Many autistic girls mask their experience for a longer period of time, but the thicker the mask an individual wears the more of an impact it has on their energy and their wellbeing and mental health," he added.
In special schools the gender disparity, with boys outnumbering girls, is most pronounced in some of the newest schools catering for autistic children.
A disparity is not apparent in the special schools that cater for children who are deaf or blind, and in the schools that cater to sick children in hospitals.
As males have just one X chromosome, they are more prone to some intellectual disabilities that are genetic.
Autism is a neurodevelopmental condition and any genetic component is regarded as complex, diverse and not fully understood.
"The latest data suggests that the male to female ratio for autism is much smaller than we used to think, that it’s closer to one to one," says Dr Sarah Cassidy, who is president of the Psychological Society of Ireland and is herself autistic.
She is referring to a Swedish study published late last year in the British Medical Journal.
The study tracked children born between 1985 and 2020 - more than 2.7 million people in total.
She said: "They looked at diagnosis rates, but they also followed those people over time.
"What they found was that if you follow people’s medical records across time what we see is that the male to female difference in diagnosis disappears."
Ms Cassidy thinks it could be that boys are being diagnosed earlier because they may have a wider array of developmental conditions that impact on how they present as babies or toddlers.
"With autism, rates of comorbidity are very high," she says.
In 2024, the Department of Education changed its thinking around gender and special needs.
Removing a weighting which had favoured boys’ schools in the allocation of special education resources, it stated: "It is now accepted that female students have a similar level of need and, in addition, it is apparent that this need is manifesting itself at later stages in their growth and development."
Special classes and schools are significantly out of kilter with this now widely accepted view.
As to why, and whether it matters, without further research it seems those questions will remain unanswered.
