To be honest though, it doesn't matter if you're a mature kid or not, as long as you study, do your homework, and make sure you don't miss school so you know when the next test is and stuff, you'll be good to go. I wasn't a really mature kid back then, when I was in 7th grade, I got 50-60's on all of my subjects. The next year (Grade 8) I decided to study more, but keep my "immaturity". Well, after that year I got over 80's on all of my subjects and I still kept my "immaturity"
They study, but again, even if you're immature, but study at the same time, you will get good grades