My husband and I enrolled our son in half-day public kindergarten at age 5 for the "social" benefits. He didn't go to preschool and was the only child at home so he was looking forward to going to school. He did enjoy some things about kindergarten but he said it wasn't very educational. He liked talking to the teachers. He liked reading his reports to go along with his "letter of the week" show & tell.
But Kindergarten is where he first learned that he was "different" because he talked more like an adult than a 5 year old and he liked to read science encyclopedias and National Geographic magazine for fun. He found that bullies target kids who are different. I remember talking to my family about the bullying problem at the school and my sister told me she felt that bullying in school made her stronger so she saw learning to deal with bullies as a social benefit. The rest of my family agreed with me that it was not. I think the school's bullying problem might have been part of the reason people at the school told us we should homeschool. An article in Science Daily
www.sciencedaily.com/releases/2008/04/080422143529.htm says Social Form of Bullying Linked to Depression, Anxiety in Adults.
In Kindergarten my son learned he had to sit "criss-cross applesauce hands in your lap" and only listen to the teacher and not ask questions about anything she read. He learned that it was important to stifle his curiosity while he was at school. He learned that singing in the restroom was not allowed. He learned that coloring in the lines was very important because the teacher said so. Kids tried to tell him there was a five second rule and if you dropped food on the floor and picked it up within 5 seconds it was okay to eat. He learned to stay close to the teacher at recess so the bullies couldn't do anything to him. Those are the things he remembers. So I guess if those things are important, than Kindergarten was good for my son.
At 10, he has excellent social skills and is comfortable talking to people of all ages. His sister (18 years older) likes talking to him so much that she calls him 4 or 5 times a day. When his sister and her boyfriend went out to eat with us recently, he was the one keeping the conversation going. She commented that he could talk about anything. She held up the ketchup bottle and said she thought he could even carry on a conversation about a ketchup bottle if he wanted to. So he took that as a challenge and talked about the actual making of the bottle and the materials that might have been used to make it (He likes to watch How It's Made) and then he went on to talk about the ketchup and I don't remember what all he said but it was funny.
I think he would have much more anxiety and much less self confidence if he were in our public school. His emotional health is very important to me.