The people who benefit are not the wealthy, who can afford to simply buy a house in the school district of their desire, but simply middle class parents who care about their kids.
Poor people care about their kids, too. They're just struggling to keep a roof over their heads and food on their plates instead of worrying about what college their kids are going to get into.
Middle class parents are wealthy compared to the average student of a "sucky" school. These schools are typically the in the poorest areas in the state/county.