Sex on the Playground

Yesterday when I picked Brandt up from school, Ms. Reed whispered to me that Brandt had said sex on the playground at recess. She said it wasn't a big deal, she had explained to him that it was not an appropriate word to use at school.
Maybe it was no big deal to her, but I was more than a little curious. Where did he hear this? In what context did he use it? Was I about to have a conversation I was NOT ready have with a six year old? Did I need to check his internet history again? He knows where he is allowed to go, but had he been searching for Kim Kardashian again?
Now I do remember a time when Ryan was probably three or four and came home school and announced to Rebecca in the middle of dinner "I know you and Daddy sex each other." The immediate question was, "Oh really, how?" To which, he responded "Because I've seen you." After much discussion we determined that to him, sexing each other was hugging and kissing - thank goodness. So I thought there might be an easy explanation.
I started the conversation in the car on the way home. Who did you play with at recess? Max. What did you guys play? Blue Angels. And he proceeded to tell me all about the Blue Angles. who Max saw at an air show a couple of weeks ago. Clearly there was no sex in this conversation.
I changed my tactic and asked him if Ms. Reed talked to him about a word that he was not supposed to use at school. He told me that he was playing with Courtney and Sofia and Courtney told him that he was a "sassy boy". Since he wasn't sure what that was, he asked her. She told him that he was a sassy boy, but he should be a "sexy cat" (and he is spelling it s-e-x-y). He did a cat move and asked her if it was sexy and she told Ms. Reed that he said sex.
That is his version anyway. I asked him if he knew what sexy meant and he said it meant pretty. We talked about not saying this anymore at school and I asked him if he had any questions. We left it at that.
The fun things we learn at school!