I was always in trouble in school because I never, and I mean NEVER accepted what a teacher told me at face value. Though as an adult I know now I went a little overboard, I ENCOURAGE people to question what they read, hear, or are taught!
Since I was not there 14 years ago when this incident happened, I can't comment on the specifics. But once you have made your point that you challenge the validity of the information, then you shut the hell up and take it up with the authority figure privately as to not challenge authority of the person, just the information disseminated. That is what the child is most likely being reprimanded for.
BTW, anyone figure out where the teacher goofed? S/he was thinking volume (Gallon/Liter) not distance. Honest mistake. The bigger mistake was not immediately recognizing the error and apologizing for the human error!
See ya
Tony