I wrote about how, despite what the president wants you think, teaching students about the history of slavery is one of the most patriotic things you can do. https://www.theatlantic.com/ideas/archive/2020/09/real-stakes-fight-over-history/616455/
Teaching the actual history of slavery does not necessitate skewing, omitting, or lying about what happened in this country; it takes only an exploration of the primary source documents to give one a sense of what it was and the legacy that it has left.
Teach students the slave narratives, show the declarations of secession, show Jefferson's writing, show letters written by Confederate soldiers, show the slave codes, show the ads placed by formerly enslaved ppl looking for loved one. These things tell the story for themselves.