Eh, it depends on the school, it sounds like. When I was in elementary school, gifted classes took you out of your regular class one day a week, and depending on your grade level, you'd do different activities that were more challenging and taught a wider variety of things than regular instruction. Part of it was completing various brain teasers and logic puzzles, but I also remember how the teachers would essentially come up with a sort of elective system, creating a bunch of self-instructed classes on a variety of topics and allowing us to pick the ones we were interested in (the only one I remember clearly is Egypt). We'd do other class-wide activities too, like put on a play for the other students or learn about etiquette by going out to a nice restaurant for lunch. In middle school, since we were on a block schedule, the gifted class was an elective you could take, and again we'd learn about things you didn't get in normal classes.
The problem that often came in was when the regular teachers didn't really know what to do with the rest of the class when the gifted kids left. Ideally, they would have taken those days to assign less new work and instead provide focused instruction to the students that were having trouble, but that frequently didn't happen. Usually they'd just keep assigning the same amount of work that gifted kids would have to catch up on when they got back (not like I couldn't do it, but kind of annoying). Sometimes they'd do special things for the rest of the class so they didn't feel left out of the cool stuff the gifted kids did, which just ended up leaving out the gifted kids from fun activities. One year, I had a teacher that didn't know how to handle me in the slightest (not in a Bob tard rage way, thank god I wasn't like him), so she just assigned me constant packets of work to do by myself in the corner. I felt so isolated over the course of that year that I was begging my mom not to send me to school. Luckily, it was only that year, and it didn't happen again.
Anyway, the point of all this is to say that gifted classes in and of themselves aren't a bad thing, but they also shouldn't be the end of a child's schooling. Parental support goes a long way, and it's clear that Bobby really needed that to help him out, although not for the reasons he thinks. It's not because he was secretly a genius that should have been in an advanced class, it's because he clearly has some kind of mental problems that he's never fully worked through that have likely been preventing him from living a happy, healthy life. Ma and Pa Chipman didn't try hard enough to figure out what was wrong, and probably consoled themselves by saying "it's just because he's gifted." The result of their inaction is a 2600+ page thread on Kiwi Farms.