People tell me every damn time we leave the house how friendly and polite my kids are and that typically kids "their age" are not as comfortable or articulate talking with adults. Other people say my kids are less safe because they are comfortable talking to strangers adults in public. I think it's just the opposite because they are not conditioned to respect someone and follow their instructions just because they are grown up. My daughter would put you right in your place if you tried anything inappropriate with her. Don't we all have to talk to strangers every time we go to a store or anywhere in public? They have friends who are older and younger and the teasing and bullying that happens in schools are things they are going to miss out on.
If you have kids, I strongly encourage you to consider homeschooling or other alternatives to public school if it's within your means.