What century was it when you first understood the brutality of the economic caste system throughout the USA?

I came to understand the American way of imposing castes...around high school if not before. The public schools lied so much and hard about it nobody missed the truth. Its only become way more ironclad in the 6 decades since then...and no more arts in schools and trade unions in the workplace to cover the lie even a little. Bummer.