Why were the first years of a slave child's life relatively good?
They didn't have to worry about going to school, keeping their clothes clean, or learning proper behavior.
The law required good treatment of slaves until they were 8 years old.
Until they were 8, slaves were totally in the care of their mothers, with no other responsibilities.
They were given plenty of food so that they would grow up strong and be able to work well in the fields.