We have a 4-week confirmation/class 101 for youth in 6th-12th grades (whenever they feel ready to make that commitment) that we offer 2-3 times per year.
We were worried about doing middle schoolers, but found they truly love all the hands on. There have been a few workshops where we've really had to update the curriculum to work w/ them (we used Potter's Workshop Curriculum), but for the most part it has been fine and the kids love it.