I agree that K can go very well. We were in a very tratidional half-day K. The teacher was fabulous, flexible and well-respected by her peers in the school. She got DS hooked up on Accelated reader within the first 2 weeks and had him reading level 4 adn 5 books while she worked with the other kids on their letters. I know she would "brag" about DS in the staff room. As a result, other teachers in the school were very excited to have him when it came their turn.
DS and I visited the K classrooms in the spring (this would be a good time)before he started. A teacher that will not let you visit is a huge red flag. I really think that his good K year set the tone for what has been a very successful public school experience.