We cover the first black congressman and many black authors (this isn’t to discredit their work) as part of the curriculum, but the accomplishments of other minorities are only really brought up if the school itself is a part of a region where those minorities are the majority or a significant part of the school population.
An example would be how Asians are only really covered during World War II with the executive order with only one person actually being mentioned as a “key term” and Hispanics are briefly mentioned in other places with the pain figures being “Pancho Villa” and sometimes mentioned during WWII but not many real names given credit other than “Mexico didn’t turn on the US”
The short, non-historical answer is that curriculum varies from district to district and what happens in one district may not be what happens in another.
The longer, historical answer is that due to the 10th Amendment (The powers not delegated to the United States by the Constitution, nor prohibited by it to the States, are reserved to the States respectively, or to the people.) and the fact education isn't mentioned in the Constitution, curriculum decisions are up to the states.
East coast schools adopted a modern curriculum in the early 1900's (literature, science, history, mathematics, art, music, physical education) and as teachers moved west, bringing their curriculum and textbooks with them, they brought their world views and perspectives. Teaching has been dominated by white women in the classroom and white men in positions of leadership, which informs which textbooks are purchased, who gets emphasized in curriculum, and who gets left out. Some states, such as California and Texas, have historically required shared resources across schools so publishers write for those states. So, if Texas history standards don't mention Asian-Americans until World War II, there's no reason for a textbook publisher to mention them sooner.