Indeed, we went to great lengths to avoid confronting actual primary sources. It's not enough to just teach alternative history, you also have to teach learned helplessness, that only certain authorities are trustworthy, and to promote a general climate of proud ignorance (looking up things in books is for losers and caring about education is for suckers).
I think you're picking a fight here that's not there: its relatively uncontroversial that there's been an aggressive campaign since the civil war to minimise slavery as a factor, particularly in the South - you will easily find "war of northern aggression" types because that is what they are taught.
All of the current FUD in the southern states against CRT etc. seems like another attempt to take control of the historical narrative to once again start feeding lies to the young and mint a new generation of unquestioning voters that believe in a false history.
No, poster is saying the schools taught them not to look at those sources, because the lost cause lie was to be taught and could not sink in if the primary sources were available (which 100% contradict the "states rights" argument taught in many schools in the US, mostly in the south)