First Day of School

Will's official first day of K4 was on Tuesday, but today was the first day that he rode the school bus. That was a strange feeling to put my kid on the bus with some stranger. I was surprised that he did so well with it all. He kept telling me that he wasn't going to ride the bus and I would just take him, but when the bus pulled up he didn't seem to mind. When he got off the bus he said that he told the bus driver to "Slow down! We are going to tip over!!" Pretty funny. He also uses the same urgency as we approach a stop sign or traffic light, just in case I forget. After hearing how successful the whole bus thing was, I was a little surprised to see a note in his back pack from one of his teachers.
It read: "Will had a rough time this morning. When we lined up to go to the bathroom, he got upset because he wasn't at the front of the line, and then refused to go after that."
I questioned him about it, and his response was:
"I didn't want to be the caboose. We were being a train and I wanted to be the steam engine."
My note back to the teacher:
"I talked to Will about the bathroom incident. He thought you were making a train. He didn't want to be the caboose. He wanted to be the steam engine. Sorry for the tantrum. Maybe in the future you can ask if he might want to be a coach or freight car as a compromise :)"
What do you do?