a problem with sexual behavior in six year old

My six year old son seams to be having a problem in school. He touches other children's behinds, tries to kiss girls, had an incident where he yelled out the word "boobies" in class, and has even been seen looking at other boys in the bathroom. I never let my son watch anything on t.v. that is not age appropriate. My husband and i hold each other and we will kiss, but not anything inappropriate. I have talked to my son many times about good touch, bad touch, even telling him he can't touch others. We have talked about how to behave in school. Nothing seems to work. His school seems to be very concerned about his sexual behavior. How should i handle this?

[rebbecca]

has anything changed in the past couple of weeks? like staying at someone house or having a play date? he had to have learned it from somewhere! do u have a baby and breastfeed or family member?
the first time my oldest seen me breastfeed all kinds on questions came out of his mouth that i never thought he would say!