I did not see where the curriculum itself made that claim but may have missed it.
Clearly slavery was different than indentured servitude, where freedom was essentially traded for learning skills or purchasing passage to the new world. The key being that for a lifetime slavery, there was no expectation that the slave could benefit outside of his thralldom. For the indentured, they had hope to improve after their term.
However, what many do not know is that many indentured contracts were illegally extended and it was indeed this extension that became a lifetime chattel for black africans who were shipped here. Slavery for life initially ONLY existed (even for black people) as a criminal punishment - and could happen to white people as well.
Indeed, the first slave for life in America who was not a criminal was owned by a black man
Anthony Johnson (colonist) - Wikipedia who himself had been indentured and then freed. He bought the indenture contract of John Casor and then would not let him go. The courts eventually (on appeal) upheld his right to keep Casor in thrall.
Take that in for a moment -
the first black slave for life in America was owned by another black man who had been freed himself and it was partially through his actions that the laws changed for others to keep black africans for a lifetime of slavery.
DO YOU THINK THAT GETS TAUGHT IN SCHOOLS? But shouldn't it be?