Black Bird,
Have you expressed your concerns to the teacher? It sounds like you have a bunch of frustrations, and talking to someone who can direct the group in the way needed.
But it's always tough being part of a team. I've done a few ballroom formation classes, and there are all different. Sometimes you wonder why people are there, because it doesn't seem like they care. But they show up for the classes and the performance, and that's what is important.
But do your best, and think of it as a life lesson on how to deal with large groups. That's called diplomacy. Encourage those who are weak. Don't always point out what they are doing wrong, point out what they are doing right. Those who think they are doing _everything_ correctly, even though they aren't, let the teacher handle them, that's not your job. Everybody likes to think they are right, and the people who think in absolutes are usually the quickest to anger, and the last to forgive. And they tend to be the ones you'll have to work with next year.
But for yourself, you care and that's great. Just understand that not everyone will care as much as you, and you won't be able to make them. One day, hopefully you'll find a class where everyone is at the same dedication level. But it doesn't sound like you're there yet. Do you're best, hit your marks and cues, and most importantly have fun. No matter what the other girls look like come performance time (you may be surprised by some of them, I know a few people who only shine when the spotlight is on them.) be secure in the knowledge that you did your best, your family will be proud of you, and half the audience couldn't tell it was lousy a performance unless you show them through body language or facial expression.
As for doing better than the baby class, please they've got one-up on you anyways. You can't beat the cuteness factor

of that age.
Good luck at the recital.
-The Ditz