Well, that didn't take long to resolve.
I had to go speak to Holly's teacher this morning on some other business, and while we were wrapping things up, I said, "Holly has really learned a lot about African-American history lately; she seems to enjoy it" (true). The teacher informed me that they are doing a block unit on Black history, because that is what the school board has decreed they will do. She admitted that she would rather take the time for more academic subjects, but has to follow policy that starting in 3rd grade, students will get a block unit on Black history.
This makes a lot of sense to me now, as we live in Little Rock, site of the 1957 Central High desegregation crisis. In fact, I was considering taking the kids down there to the museum next door to the historic school myself-I think they're old enough.
(There is an irony around that school. When it was built in the 1920's, it was the new "white" school in what was then a posh suburban neighborhood of Little Rock. It remained so for over thirty years. Today, it is considered "inner city", and is one of the most segregated schools in the state.)
Thanks for all your input! I'm glad I didn't go in there with guns blazing.