I pulled my daughter out of kindergarten and put her back in a daycare she liked. She had come home crying every day for the first week, but because she was used to interacting with new adults and other children, I didn't think it was the newness of the situation. She thought the teacher hated her.
Even with a parent watching, that poor retirement-age woman was so burned-out and crabby I couldn't believe she still had the job. She yelled, insulted, sneered at and bullied the whole class for the hour I was there, and I was truly afraid my daughter would be emotionally scarred. I told the office staff why I was removing my daughter, starting immediately. I didn't want to threaten that teacher's job, but her behavior was a long way from professional. I never heard further about the issue.
Interestingly, this month's issue of The Science Teacher magazine has a news feature about how bullying can, indeed, change a young child's nervous system by altering the behavior of a gene. The result is a body that produces less cortisol, the stress hormone, but increases the likelihood of mood and behavioral problems, including aggression and depression, by the time the child reaches the age of 12. Here's a link to that press release: http://www.eurekalert.org/pub_releases/2012-12/uom-bbc121...
Other than that, my daughter had pretty good to amazingly wonderful teachers, and nobody else who scared her. At home, we also did lots of enrichment activities, which we both enjoyed.