Edit: I just realized something, here's an idea, why not just expand the good high schools, and let the parents/kids choose which high school they want to go to. Why should we have failing high schools that continue to operate? Same with the colleges.
So, a couple of problems. First, not all students are the same. The same style of teaching probably wont work on all students, so expanding certain successful ones would only be beneficial if all students were the same. Second, the successful schools have WAY more money going into their coffers. If you expand those high schools to cover more and, most importantly, poor students, the money per student ratio will go down dramatically. I.e. the successful school is only successful due to the fact that they suck all the money out of public education... just as they suck all the successful students out of the public system. Most have such high entry levels, you realise that the school does NOT have to do a single thing with the children and they can class themselves as successful. So third is that they BUY their success, not actually work for it. Lastly, rich parents will not want to 'waste' money on poor children as 'shown' by people like Charles Murray (who people like Sam Harris, Joe Rogan and Bret Weinstein think he has a point, mind you. Only rich people should have money because them being rich means they can handle money.)
In other words, its all a façade that has no substance to it and will break immediately if you try to expand it to other children. Most of this has got to do with there being no one that has any incentive to look after poor students. That's what you need to target.