You sound like you are describing my son when he was that age, I even looked to see your location because it sounded so similar to his pre-k. He's 7 and in 2nd grade now. He went to the same day care/pre-school from the time he was 7 weeks old until the summer before he started kindergarten.
Everything went well from the time he began until he started pre-k 4. He had the same teacher when he was in the 3 year old class, so I didn't expect any problems when he was 4. At the end of November of that year, his older teenage half-sister moved out of our house unexpectedly after a fight with her dad. He started misbehaving about that time, but December is a hard month on kids that age because of all of the excitement of Christmas, we just chalked it up to that.
When January and February rolled around he was still having trouble sitting still, cooperating, participating, etc. that they began to call me almost daily about it. I tried every thing possible to get him to understand his behavior was wrong. At the beginning of this time a new child had joined the class, who the teacher confided in me that his parents didn't make him mind at all. Of course, these two were instantly attracted to each other and wanted to be friends. Along about March we finally got things under better control. They changed the two boys up where they weren't in the same group. And, a male teacher came in as the assistant. We also began seeing a child psychologist.
Everything rolled along fine until the last couple of weeks of May. Suddenly, I was getting daily phone calls, this time to come pick him up he was being so unruly. I worked a block and a half away and they knew I could easily get over there. By Memorial Day, they had decided he could no longer return to the school.
As one of the posters below stated, she found out her son was gifted. Though my son has not tested gifted (mainly I think because he has had such trouble learning to read), everyone in my family thinks he is. My mom was a teacher for over 30 years and is GT trained and administers the test for the school every year was the first to point this out. He is very creative and has the most vivid imagination I have ever seen.
BUT, he has also been diagnosed by the child psychologist as ADHD. When he was seeing her, she theorized that maybe the abrupt way his sister moved out of the house was part of what triggered it. He had always been active, but no more so than what I thought was normal for a small child. However, his father and the half-sister are both ADHD. So, it didn't surprise me when he was diagnosed with it. My husband and I did not want him on the narcotic prescription medication. I found a homeopathic medication, Attend, at our local health food store that he has been taking since he was in kindergarten. It does not have the side effects the narcotic prescription meds have. He does well on it.
I think it is so hard on kids these days, they are forced to learn so much so early, it just seems to put undue stress on them.
I wish you good luck and pray that things will get better for your little one.