Since the Obama daughters both attend a private school, it would be politically foolish and embarrassing to deprive poor children in DC from attending private schools.
It hasn’t stopped any of them in Congress. All of them send their kids to private schools here, or keep the kids in their home states so as to avoid DC schools. They are shameless, even when called on it.
But that's what he's doing, the program is closed to new entrants. The media won't call him on that, they'll rave about his compassion.
Imagine having one kid in the voucher program but having to put your younger ones in the DC Public School System. This would be a great research project, comparing the siblings that were grandfathered in and their younger siblings. I think I already know the results of this study.