Why did Calpurnia request Scouts presence in the kitchen?

I think you are talking about the moment when Scout
criticized Walter Cunningham for putting too much syrup on his
food.

Calpurnia wanted to point out that it was
inappropriate to criticize company and that we should respect all people's ways.
Fortunately for Scout, Cal chose to do this privately. This is why she called Scout into
the kitchen. She tried to scold Scout for this behavior privately. This may have been
done to respect Scout or to protect Walter's feelings. Maybe it was done for both
reasons. Whatever the reason, it all shows that Calpurnia is sensitive to all people's
feelings.