My child is in our self-contained gifted program. In middle school, it's been great. They are in Algebra I in 7th grade (well, it's called something else due to common core), Spanish 1, orchestra, gym, and then the self-contained gifted program for Science, English, and social studies.
I would say that the most important thing in middle school has been:
1) Learning how to manage your time well. Most of the homework assignments are easy, but they have time deadlines. Things have to be turned in on time or you lose points.
2) Walking to 7 different classes daily, on time.
3) Making new friends, socializing.
To me, middle school is an organizational challenge for my child, not really intellectual.