I personally went to a Public School K-3 and Private 4-12...what a difference! Sure, there are still some "bad" kids in Private schools, but the school does not HAVE to tolerate it. Parents are paying their hard earned money (while paying taxes for Public Schools) to the Private schools, so not only do most expect thier kids to behave in a certain manor, they expect the school to handle the kids with behavior issues.
Our kids are in a Montessori school now which I would consider a Private education. We live in an area with GREAT schools, but I still beleive my kids are in a better enviornment from MANY aspects. In each classroom, there is a Peace corner. So, if Mary says something to Johnny and Johnny does not like it, off to the Peace corner they go. At this point, they talk about what happened, how it made them feel and they apologize for their behavior. Nice. If a child is disruptive (talking during a lesson, playing with the velcro on his shoes.....), he is removed from the area and talked to about his behavior before he can return to the group. Bottom line, they are there to educate and any child that is trying to prevent that from happening is addressed.
Kids are going to be kids, but I think (from my own experience and that of our kids) the enviornment, the teachers and the parents all play a roll. Parents are BUSY and soem send their kids to the Public schools because it's free and they expect the teachers to do it ALL. In a Private school, parents have high expections for school AND at home behavior. That consistancy makes a BIG difference.
All Public schools have good kids too of course, but sometimes they are "over looked" because there is soooo much focus (from the class adnd the teachers) on the troubled kids.
Good Luck...it's a hard decision to make!!