The Elements of Euclid is a model of clear, concise, beautiful mathematics which is easily accessible. Archimedes as well. Follow that up with Apollonius, Ptolemy, some Descartes, and then Newton, and you have a junior high and high school curriculum in mathematics that would give students a real advantage over the rote "here is what Disembodied Authority says you should know" learning.
Note -- I am not advocating the study of mathematical history in junior and high school, but rather the study of mathematics historically. It gives access to mathematics as a branch of the humanities, less focused on the answers, and much more focus on the questions and how some really smart people have addressed those questions in the past, which gives a good guide on how to address new problems that will come up in the future.
When it comes to history specifically, as the OP asked, I would still agree with going with some of the great works of history. Historiography can be left for college, but give the kids access to the letters and diaries and personal accounts of people who were at the scene of history, as well as the great works of history that have been written (Thucydides, Herodotus, all the way to Toynbee, Gibbon, and, hell, even Spengler). Drop the mundane and milquetoast textbooks.