If you can really afford it (take an honest look at the sacrifices and whether they are sustainable in the long run) I would move both.
As platypus says, I�d also take an honest look at how much worse the situation could really get for your DS and whether the new school might be as good a fit for him as for DD, but I have to say that a school deciding to meet the needs of intellectually disabled children with violent tendencies by moving them two grades down would be a huge red flag for me!
Agree that some choices can�t be up to 5 year olds. If you feel that the more expensive school suits him well and the sacrifices don�t impact him (or other family members) unduly, I�d move them both.
