Comment by tstrimple

In my experiences with them, prior to high school they just amount to a few additional worksheets on top of existing assigned work. In elementary school, my girls were pulled out for about an hour a day to go to another room for their "advanced" classes. There was no advanced instruction. Just more math worksheets. It's not really until high school where you have real AP classes that involve actual teaching and not just isolation from the rest of the kids. My experience was much the same, but I actively didn't have friends so enjoyed the isolation at the cost of a few worksheets. They did nothing to actually help us "advance" though.