I'm not sure of the necessity of teaching about stereotypes to an 8 year old, but of course talking to them about confiding in an adult they trust if something's made them feel uncomfortable is of the upmost importance, and IMO needs to be done in conjunction with parents.
As parents, we felt it was our role to teach our children to respect others and to be open minded about and tolerant of others, and their school to reinforce these values, rather than abdicating our parental responsibility to the school. The same applied to sex education.
There may well be cultural and or religious factors in a child's family that would determine for example at what age those discussions should take place and the content. Which is why, although I don't know if this is the case, and how practical it is to do so, parents should be informed before this takes place during school.
When education was confined to the basics, life must have been so much simpler for parents, teachers and children of all ages.