I don't mean to nitpick, Tom, but is this really your plan?

But the story is explicitly about beauty, not class (and contributes to the confusion between those two--ugly "means" "wrongly categorized," which is great if the issue is whether something is a really bad chair or a really good table but not so good as an analogy for people). I think the story is trying to teach "don't mistreat people who don't fit your definitions of beauty" but it fails because the reason is "because they might end up more beautiful than you." It matters how the ducks treat the ugly duckling because how you treat vulnerable people is an important part of character--and I totally agree that the ducks would suck up to the swan!