There is no absolute answer here, but here are some things that might be helpful to her:
"Placement" is the term that deals with where the child will be educated.
34 C.F.R s 300.552 states that placement teams must identify the placement that will allow the child to be educated with nondisabled children to the maximum extent appropriate.
That is the mandate known as the least-restrictive environment (LRE).
To that end, the placement team must first consider whether provision of supplementary aids and services will permit placement of a child with a disability in the regular education environment, rather than a more restrictive environment, such as the home.
However, no one factor makes the decision on placement, although parental input is given great weight.
So, the school needs to do what it can to teach the child in the regular ed classroom. If he needs a device, such as this machine, to be included in the classroom, and that is the only thing holding him back, then the parents have a strong argument for getting that issue handled in the way they wish.
I would advise your sister to contact an attorney who focuses on special education law. It might just take a phone call or two to get the school to do the right thing here.