I would suggest that because history tends to take the perspective of the writer, much of what is in school texts is already biased.

When Olive P Dickason wrote "Myth of the Savage" she demonstrated clearly that the Iroquois had a functioning democracy in mid-eastern Canada and north-astern US long before Europeans ever came here. That is largely ignored.

I know of fewhistory texts used below undergraduate level that fairly treat Blacks, Mexicans, Asians or Native North Americans. Much of what I can gather from Arizona (and elsewhere) is that those in charge deem studies that present a White perspective to be quite alright. Other stuff then becomes so-called "ethnic studies." How quaint.