It has nothing to do with "middle school" and everything to do with age. It doesn't make a difference if the kids are K-6, 7-9 or K-5, 6-8, etc. It is TOTALLY the age of the kids. It is mainly hormonal, especially for girls. Educationally the learning styles of 6-8th graders are much more consistent so it makes sense to have a "middle school".
Could've fooled me this morning! But I'm truly glad to hear that she still likes school!
and kids are more mature.