New England has a very complicated attitude towards public education. They did a lot to pioneer it in the 19th century and even before that, but mostly neglected public higher education for a century after that at least in comparison with the Middle West. Neglect of charter schools and magnet schools may be part of the same pattern.
Also, everything is divided up into towns with their own established bureaucracies and monopoly advantages. Elsewhere something might be done at the county level or in some other way. You do see vocational-technical schools on a multi-town basis, but nobody's challenged local public schools with an academic magnet program.
It's a pity. Some of the regional high schools in the wealthier suburbs are very good, but they don't really push or inspire students like some of the ones written up in US News apparently do. I don't get the feeling that they see the need. All the children are already "above average," so why bother?
The other side of the coin may be a higher tolerance for private preparatory schools. Elsewhere, parents might get together and form a charter school. In New England they try to get tuition together to attend an established private school.
Why New Englanders don't go in for things like the International Baccalaureate, like these other schools, I don't know. I've never heard of such a thing apart from articles like this. And schools like Boston Latin and Latin Academy are examination schools and don't make this list.
It's not for lack of trying on the part of parents. The teachers unions are VEY powerful here, and they block almost every attempt to open new ones. They seem to think that if people have a problem with the public schools, that it's THEIR problem, it couldn't possibly be the schools' problem!