Why did school authorities want this mural painted over?

A reader sent me a link to the following story. Liz Bierendy is a 17-year-old student at a school in Rhode Island in the U.S. She painted a mural for her school depicting the progression of a boy from childhood to adulthood. Have a look at the mural below:

Pilgrim High School mural, Warwick Rhode Island, by Liz Bierendy

It seems that school authorities saw the mural and felt it to be offensive. They ordered that part of the mural should be painted over.

Can you guess why? Here's a clue: the "offensive" part of the mural is the bit at the end.

The authorities did not like Liz Bierendy's portrayal of the family. According to Liz Bierendy she was told that portraying a man getting married to a woman and forming a family,

may be offensive to some people because it is not how society views a family anymore because some people may not grow up with a mother and the whole marriage type thing may be a religious symbol.

I am tempted here to write "Really?" about a thousand times. But I should know better. I have explained in detail myself why liberals have issues with the standard traditional family. I shouldn't be surprised if liberals treat seemingly innocent depictions of the family as being too suspicious to be rendered into art.

The mural was only saved when a higher official, a school superintendent, stepped in and used his authority to allow the mural to stand in its current form:

The section of the mural featuring the family was ordered painted over by school officials. Bierendy said she was notified prior but she was still "pretty upset." The Superintendent of Warwick Schools Peter Horoschak has since stepped in and asked that the student be allowed to finish the mural however she sees fit.

Bierendy says she is going to take the weekend to “think about this,” and on Monday she will decide how to finish the mural.

In a statement released by Superintendent Peter Horoschak he said "some of the members of the Pilgrim High School community suggested that the depiction of a young man’s development from boyhood through adulthood as displayed may not represent the life experiences of many of the students at Pilgrim High School."

Update: I've just read some comments in a local newspaper about the issue. Most readers are supportive of the mural, but those few that are against really do believe that the mural is an attempt to impose religion or "religious values" in public schools.

Is the American left really going to go down this path and view the family as a "religious symbol" that must be kept out of public life?

It's a serious development as a society needs a stable culture of family life to prosper, but public authorities will not be able to promote such a culture if it is deemed to be a "religious value" that cannot be favoured within public settings.