My experience is they like to spread the bright kids out evenly because it makes it easier for the teachers. The one time they did put 3 gifted kids in one class they only allowed 2 kids from each class to attend extension programming. You only have 2 classes though and the sound less crazy. Just saying what seems logical to you may be the opposite of school practice.
Yes, this was the feedback from my mom as well, who used to teach elementary.
There are elementary schools in our county that do gifted clustering, but they tend to be very big. In that case I get the idea that there are enough high performing students to go around, so the teachers don't feel much of a drop off getting the second tier of advanced students. The one I know that does a good job of it has 6 K classes.
