It is not unusual for there to be discrepancies in text books within the same country. I recall an interview with Desmond Morton who wrote most of the Canadian High School history books. He said that the BC government requested that the paragraphs on the internment of the Japanese during WW2 be removed. They remained for Ontario and other provinces.

Canadians need to be less sanctimonious with respect to the US. The US black community also needs to acknowledge that;
1. Slavery was a global issue until the mid-nineteenth century
2. There were white slaves as well, they were in high demand in the Ottoman empire
3. Their own people greatly assisted in their capture and transfer to America.