What's the F word?

Okay so I started working at my kids school less than a month ago and it has been going really well, but today tried me a little. My 8yr old has been throwing up and lunch today was two of my least favorite foods to clean up mashed potatoes and corn muffins so lunch already was on my last nerve. Then two sixth grade boys got in a semi fight of which I had to take them to the office cutting down on my very cramped and precious time of wiping tables. Then I finally get out of there only to be met by my fellow DUTIES!! as we are referred to, and the look on their faces let me know that I was about to hear a good story especially when they asked me if I was listening to the walkie talkie's so I knew it was going to be good. Little did I know!!!
They informed me that my son Brody, was caught on the playground saying the F word yes that is right. my sweet angelic son was dropping the F bomb on the playground. Now in all seriousness he really is sweet and this is that last kid I would expect this from. My 4 yr old however I expect him to be in trouble the first week of school.
Now here comes the funny part, he was told on by some kids and so the duty went to confront him on what he was saying, so she asked him if he was saying the F word and he proceeds to ask her "What's the F word?" and just so you know we are not allowed to tell the kids what the words are. Luckily there was another child there to spell it for him, to which he responded yes that is what I said, (he doesn't have my flare for lying@!) and then proceeds to tell them why he said it so at least he was using it in the right context. So needless to say we are going to have a little talk when he gets home!! Any advice let me know!!