It had to be more than just one person. The trial that was already held pretty much determined that. The principal was the original person that she said told her she couldn't bring a same-sex date to the prom. And she said that she asked him, specifically because the rule had been there in the past. So obviously, it wasn't a just this year thing. Also, in one of the articles I saw, but can't seem to find again, the judge made note specifically on the fact that some school officials testified that they canceled it due to the disruption caused by to the learning environment, yet the principal himself testified contrary to this, saying that the learning environment wasn't disrupted.
Lesbian gets day in court over nixed prom - USATODAY.com
McMillen vs. Itawamba County School
Note, it was the county's school Superintendent Teresa McNeece that was actually said to have canceled the prom. And the School Board Chairman Eddie Hood certainly testified for the school, because he is the one who said that there was another prom sponsored by the parents. Also, there was rules put out for prom that included that couples could only be opposite sex couples and that girls had to wear dresses and boys had to wear tuxes.
You're wrong. It was the school district officials, multiple, not just one administrator, that were guilty of discrimination and canceled the prom. Also, the mayor of the town defended the actions of the school board, saying that he supported the decision. This isn't just one person.
I will admit that I was wrong about the ticket price issue. From the link that I gave that has the actual court documents, Exhibit A (p. 10/20), says that a guest is someone outside of the Junior or Senior class of that school. This means that most likely it is because her gf is a sophomore that she had to buy her a guest ticket. But that does specify that guests had to be opposite sex. And this memo was written by Mrs. Sandy Prestige and Mrs. Sandra Sabino.