It's only white racist "conservatives" who object to the teaching to America's true history. My own learning about how and why black people got here, why we were and are always at the "bottom of the well", began at home and in Sunday School at the oldest black church in my town, founded in 1919, during the terrors of the Red Summer of 1919.
None of that history was told to me by the "public" grade school, "public" junior high school, or the "public" high school from which I graduated in the top 10 percent of my class.
In college (Indiana University), I was a part of the then minuscule black student body which protested and demanded that IU institute a "Black Studies" curriculum. That program today offers doctorate degrees and is one of the most respected in the US.
Teaching objective history is not "bias" --again, unless you are a white conservative racist.