When judging any two people, do you claim to be privy to every single detail which they can be judged on?
I can’t think of any constructive purpose to deciding who is a greater gadol (with exception for piskei Halacha- not the discussion here). We choose people and specific traits to emulate. When comparing two people, by default, one of them will be considered lower which seems very inappropriate with regard to people of a certain stature. (Lashon hara possibly?) Furthermore, even when we are judged, we are not compared to a gadol, we are only compared with our own potential.
There is a great line that anyone can count the number of seeds in an apple, but only Hashem can count the number of apples in a seed. This discussion feels like children (WADR) choosing apples by number of seeds.
In a nutshell, IMO it seems disrespectful for the schoolchildren to be discussing who is a better teacher, and doing it in front of the Principal. I guess it’s a sensitivity.