I can't say this was the case for your school, but often certain events or changes in culture cause rules to be established that end up being incomprehensible years later.
For example a shaved head was ok when I started school, but when neo-nazi skinheads became popular in the '90s the haircut became unwelcome (though not strictly prohibited).
Beyond the observational evidence: that fact that every culture to ever exist in all parts of the planet value some degree of conformity, the conceptual points are just as strong: efficiency, harmony, unity, happiness and many other traits are higher in more uniform groups.
What if everyone in the classroom spoke a different language? What if everyone in the classroom had a different set of values and ethics? These commonalities ARE a degree of conformity, and they made interacting and the rules of engagement clear and simple so more important things can be focused on.
Obviously there are drawbacks: if everyone was the same person then there’s nothing new. One could argue that everyone having the same religion is worth it because now everyone has more in common to agree on, one could argue that removing that freedom comes with too high a cost to the new and interesting.
In summary, conformity is certainly useful, but comes with side effects and drawbacks.
LOL, yeah right.
"WHAT?!There are still BITS OF PLANT IN THIS HOLY MUSTARD! BLASPHEMER! Knights of Lord French, SEIZE HER! 'Stone ground'?? WHAT HERESY IS THIS?! The Book of French's, Chapter 8, Verse 3 clearly states, 'Our Lord French, who blessed the world with bright yellow smooth mustard, hath decreed all other mustards to be a blight upon the world!'
You will face trial by hot dog eating contest. Lord French will judge your pitiful soul..."
This is weirdly specific. Were there any gypsies?
Here's a list of bizarre things that my school in Belgium was intolerant about back when I was in school. These are just the ones that come to mind right now, there were many others.
1. No short hair for girls. No bald boys. No dyed hair.
2. No piercings for boys, and only pierced ears for girls
3. No hats. No shorts.
4. No long skirts for girls. No short skirts for girls. Only between knee and calf length or some such bizarre nonsense.
5. No skirts for boys (I tried a kilt once, was not appreciated).
6. No rings for boys. Not "too many" rings for girls.
7. No sitting in boys' laps. Except when you're a girl sitting in another girl's lap, that was apparently fine.
8. No tops with straps thinner than a finger (for girls, I guess).
The problematic gendering aside, all of those rules always seemed bizarre and stupidly specific to me. Did a pierced bald boy with a ring once torch a school? Do teachers have some kind of phobia for specific hairdos? I get that it's a conformity thing, but conformity never struck me as being useful.