My scenario of reading the class a book could be part of the reading language arts curriculum. The students could compare and contrast the families in the book. They could make text to text and text to self connections. Those are all a part of Core curriculum. Then students could then use the book as inspiration to write about their own families. Many lessons could be taught as an off shoot of this read aloud.But why does this need to be taught? Where does this fit in with Math Science and Reading? Schools are not there to promote religion or different lifestyles. They are there to educate kids in Math Science and Reading.