This seems to be a trend in the UK and in Australia and I would be interested to know if it is a pattern around the globe. Any references to articles (in English) would help with the the evidential aspect.
Yes, there are more children attending special school who are able to do so, but there are many more children who are either go to special schools or main stream system due to financial problems.
As far as I know, the No Child Left Behind Act passed by President Bush here in the United States doesn't allow special schools for special needs except in dire circumstances and not typically until high school. We do have special education teachers who work with kiddos in special education classrooms within the school but not specific special education schools, unless it is a private school.