My son is in a gifted middle school program where each grade level has ONE group of 23 kids. In this group of kids all the gifted kids are placed in the group and then they fill in up to 23 with additional non-identified kid who they think can hack it (but don't have the testing). Those kids have to apply to the program with an essay, recommendations, and application. At one point this was a middle school IB program but at some point they dropped that and made it this program.
This group of kids travels together from class to class as does a cart of Mac laptops. In this particular school it has been a godsend for my rule follower, quiet kid to be in class period after period with students who are high achieving and highly capable and deep thinkers. When put out into the wild mix of kids for electives, those classes been very stressful on him. Not that his academy kids don't ever act up but when you say do something and stop talking...they stop talking and do it. Or if you say talk about some particular thing, they do what you asked and only have to be minimally redirected from talking about hair or One Direction and they are not rude at all.
And I know for certain because I worked at the school last year and subbed for his class and tons of other classes.
Not all of the kids were globally advanced but they all had the ability to keep up, some having to work harder in one area than in others.
They do the regular curriculum at an honors level but a bit faster on the regular stuff because they learn faster which gives them time for additional projects, individual and group. They do tons of extended learning and projects.
Their electives are all different but their core classes LA, Math, Science and Social Studies are together. The school also has a Reading class that is mandatory and 6th and 7th grade they had that also...but it was officially labeled as an elective (a no choice elective). This year if you have a 5 on the NCLB testing (scale 1-5) in 8th grade you didn't have to have reading. His entire academy class had a 5 and so they made them up a creative writing class so they all have that elective together (it was supposed to be a mythology class but at the last minute that was changed to creative writing).
Long way of saying they have self-contained all the gifted kids and then filled in to make it a full class. They move quickly through the background learning which allows for lots of discussion, projects and extended learning. All of the teachers are gifted endorsed OR are making progress on being gifted endorsed (I think it is either 3 or 5 classes you take and then add it to your certificate in addition to your content certificate). Math is Algebra I in 8th grade with high school credit and Science is Physical Science in 8th grade with high school credit. There are a few other sections of both of those classes that aren't a part of the academy but the majority of the school is taking pre-algebra in 8th and 8th grade science.
