Update...We ended up staying for 2 years of preschool at that school. We also compromised with DH and she only went to school 1 day a week. That was what she was comfortable with. I would have been fine with her not attending at all. After the one particular older girl and rough boy left the school to go to kindy, things changed dramatically at the school. The one leader of the pack girl, was experimenting with power issues as the older sibling of a new baby, come to find out, and some other emotional issues regarding her family life. Some of the boys in question, simply introduced my dd to violence not experienced before among our friends and family. We don't watch TV, so we don't get exposed to much of that, and we don't model aggression and yelling. There were still a couple of rude or rough kids this year, but she was less affected by them and better able to defend herself and others when needed. But, not because we spent more time at preschool, as some posters suggested would benefit her "fitting in."
By the end of the school year this year, I was not attending with her and she had forgotten any anxiety that she once had for me to leave her there. But, not because of anything anyone else did. The teachers did not intervene more, the environment, while less distressing with the older kids gone, still had a few cliques of kids whose parents spent time together, and therefore knew each other outside school. But, she came to understand through our conversations that the shortcoming was theirs not hers. She found and nurtured several relationships with other children, particularly a couple younger kids who were lost at sea there, and became a leader. I think the shift came from accepting and listening to her concerns and need to be connected to me at home more than to be at school. When those needs were met, she was able to be confident and successful in the preschool setting, or any other setting for that matter.
If I were to do it again, I would be less hung up on what other people thought I should do--(preschool is not necessary or better than being in a rich and educated home environment) focus on my intuition, be willing to argue harder about it with DH, trust my daughter's development. I would not tolerate the attitude that children need to learn to socialize with each other on their own terms..."that's just the way things are." Our job, and that of teachers and caregivers is to provide the guidance and tools with which to relate to one another.
I spent a lot of time worrying because there are so many cultural messages about forcing independence upon children for their own good. It didn't sit right with me, and if I had more confidence in myself, I would have spared my dd the experimentation and us both the anxiety.
Someone in this thread recommended the book, Hold On to Your Kids. I read it and am grateful.