For a long time now US conservatives have been OBSESSED with concentration of wealth. They've been busting their butts to think of new ways to take money from the middle class and give it to the top 1%.
Charter schools are perfect for this. Everyone pays for them, meaning 99% of the funding comes from the middle class, but the richer you are, the better chance you have to get your kids into them. Plus, being private, you have taxpayer money going to corporations--which cons love!
Plus, cons hate public education anyway. Partly because they hate public -anything-, but also because most public school teachers are unionized and they HATE that! They hate the USPS for the same reason.
Finally there's the conservative concept of 'meritocracy'. 'Meritocracy' means, simply, that the rich are more entitled to good things than other people. They believe in 'school choice', meaning the SCHOOL has the choice. Private and charter schools can pick their own students, they can pick only kids with good scholastic records already. Then after a year or two they can show that their kids do better, on average, than kinds in PUBLIC schools, because public schools have to take all applicants. This, of course, justifies the govt. spending more taxpayer dollars on things only the rich benefit from. They call this 'meritocracy' because 'moneyocracy' is not a word.