While some vouchers are based on this data shared elsewhere in this thread indicated that most are not. Outsourcing disabled kids to a specialized school has a number of disadvantages and is not a program I would broadly support. I think the most notable is that it reduces the interaction of the typical student populace with disabled students causing them to be less aware of the challenges and issues they may face. A lot of education is exposure to different peoples and perspectives. I had a disabled child in one of my classes at a young age and think that experience helped develop my empathy for people who had a different experience of life than my own. If the benefits to disabled students are sufficiently large they may outweigh the gains to the broader student body but designing systems to be insular rather than reflective is something that should be done with an abundance of caution.