Bad mom moment

So last night I was at my weekly volleyball game with several friends from my neighborhood when one of them asked me if Adam was late for school the other day. She said that after she dropped her kid off one day last week she was driving home when she saw Adam running up the street as fast as he could go. She knew that her son was late, because she is running late practically everyday and we make fun of her for it. She thought it was funny that her son actually made it to school before Adam did, although they were both apparently late that day. Even though we live less than a block away from the school I usually drop Adam off on my way to work, but I was home sick one day last week so I sent Adam out the door on his own. While I was standing in the doorway watching him go I heard the bell ring so I told him to run, run, run so that he could beat the tardy bell five minutes later. None of that is the bad mom part - here it comes. Here we are at the end of February and Adam has been in school since September and just last night I found out that I was completely unaware of when the morning bell rings. According to my volleyball friends, the bell that sometimes is going off when I drop him off or when I am standing in the doorway watching him walk IS the tardy bell. I have been five minutes behind all year. Good move, mom. That explains why Adam sometimes comes home and tells me that all of the kids said hello to him when he got to school. I thought they were just friendly, but in reality his teacher apparently has the class shout "Hello -insert kid's name-" to any latecomers. The embarrassment hasn't been much of a deterrent for either of us though, because Adam loves the attention and I was unaware of any of it.