Charter schools are not self-selecting, they have to accept everyone who applies up to the number of places available, if more people apply then there are places available then they are required to have a lottery to select students for places.
You have to apply and pay and jump through hoops to get your kids into them
Charter schools are not permitted to charge an entrance or application fee.
the children who have mental, emotional or learning handicaps.
To cite one example Harlem Success Academy actually has higher than the average special needs students compared to surrounding public schools. In any case they must accept special needs students to get a charter, again this idea they somehow get to pick and choose students is just FUD organizations like ACORN, AFT and NEA publish.
Lastly, flight from public schools weakens the resolve to do something about it. For example, if the kids of politicians aren't in public schools then there's little incentive for them to seriously work to improve the situation.
There is no resolve to fix the system, they have had decades to do something about it and haven't. Asking us to continue sacrificing children to a system that fails them on the hopes that maybe someone will fix it is both repugnant and the opposite is suggested based on the history of attempted reform.
Also on the issue of vouchers and private schools I consider it hugely advantageous to provide a mechanism for highly performing students to have a curriculum and environment that nurtures their abilities instead of one that seeks merely mediocrity. While it might make us feel all warm and fuzzy dedicating more resources to students who are failing is insane, teach everyone up to a base but provide a mechanism for those who can go beyond that base to do so.