Is it permissible to desecrate the American flag for educational purposes?

It was a one-day exhibit at York High School on Sept. 26. 
Staff members from the English and social sciences departments placed an American flag on the floor in the school’s library as part of a project on First Amendment rights.  Students were not permitted to walk-on or deface the flag.

The school gave the defiled flag to the American Legion so it could be properly retired.
A spokesperson for the Elmhurst Community Unit School District 205 told the Chicago Tribune neither the school board nor district administrators were notified prior to the display.
Well, I suppose we should not be surprised that a bunch of public school educators decided to desecrate Old Glory.
“It was used for students to reconcile their feelings about current issues and whether their First Amendment rights are protected,” Principal Erin DeLuga wrote in a letter to parents.
“The purpose of the forum was to explore the complexities of the constitutionally protected right of free speech by examining real cases,” DeLuga added.
The library desecration was a recreation of the 1989 Dread Scott’s “What is the proper way to display a U.S. Flag” art exhibit. The original exhibit included a desecrated American flag.
“This is in no way meant to disrespect the flag, the military or the government,” the principal wrote to parents.
Parents and students were outraged by the school’s un-American exhibit.
“This is just plain disrespectful,” one school alumnus wrote. “I was taught at a very young age the flag never touches the ground. Never! I am so upset at this sorry excuse for educating today’s youth. “
“I am appalled at this form of teaching,” another graduate wrote on Facebook. “You say that this in no way was mean to be disrespectful, but in all reality it most certainly was.”
“Your staff is disrespecting our American flag,” wrote a York alumni who served in the military. “My grandfather,  a York alumni, fought in World War II – risking his life for that flag you put on the ground. Want to teach freedom of speech – disrespect a Nazi flag.”
Surely there must be some other way to teach the children about their First Amendment rights that does not involve desecrating Old Glory?
Of course, there were supporters who praised the school for defiling our flag.
“I’m a proud York graduate today,” one woman told the Tribune. “This is ONE example of democracy in action,” said another.
I wonder what would’ve happened to teachers if they had desecrated a rainbow flag for the sake of teaching kids about their First Amendment rights?