Why did a French school think color-coding students who don’t eat pork or meat was a good idea?

Why did a French school think color-coding students who don’t eat pork or meat was a good idea?
French Muslim student banned from school for wearing long black skirt.
Secular atheist jailed for grenade and shooting attack on a French mosque.
A Message From the Dispossessed Chris Hedges on Roots of Terrorism and Free Speech Hypocrisy
Kebob shop bombed and mosques attacked in France after Charlie Hebdo killings.