Even if the custom of always lining children up in school from the shortest to the tallest has a reasonable utilitarian purpose, it still could be problematic for those children who are sensitive about their height.

I was a middle kid-meaning my last name was in the middle of the alphabet, and I was mid-range in height. But you don't have to be the "victim" of a custom to see & sense how that custom can and does {and did} negatively impacts other people.