Hey!!! Good to find someone from Brazil here! I'm Brazilian too, and I was a tour guide some years ago. Took those HUGE groups to WDW in July... (I was the FLAG LADY...) They drove me nuts and I gave up being a tour guide. LOL
Well, you are absolutely RIGHT!!! Generalization will not work at all...
First of all, I completely understand your feelings. You have no idea how hard it was to try to control those kids for 15 days, usually taking the blame and listening to lots of complaints as if I had done horrible things. And many of them were not interested in WDW at all, didn't want to do anything except going on thrill rides, singing, dating, and partying (far away from their parents, what a great opportunity! LOL). It was a very frustrating experience to me.
However, there are some points I would like to clarify:
"English is a mandatory subject in private schools in Brazil starting at a very young age and is seriously drilled into students and taught for a few years (its entirely different than the horrendous second-language teaching in the U.S.)."
Yes, English is mandatory, but NOBODY learns anything at school. Classes are poor, students don't really want to learn, and the syllabus doesn't include much more than numbers, colors, the verb to Be and some very basic vocabulary. (just like the horrendous second-language teaching in the U.S.) I am an English teacher myself. I don't work in regular schools, I teach Brazilian adults how to speak English. I work for a Language School.
"In the Latin American culture, it's traditional for girls to celebrate their 15th birthday with a big party. From what I understand, in Brazil, the kids take a special trip instead of the party."
Yes, that's true. We have the special party, but it is very common for girls to have both the trip and the party. Some middle class (or even lower middle-class) families save money for years to send their 15-year-old girls to WDW. They often prefer the trip instead of the party. It's like a once-in-a-lifetime opportunity for them.
Fell free to ask more questions, if you are interested in trying to understand the BTG, ok? I'll be glad to answer!
Anyway, it's great to be here!