Should I teach CCD/Sunday School?

I'm not sure what CCD is and I've never taught Sunday School, but I recommend you get as much teaching experience as you can get. It sounds like it'd be more low key than any traditional classroom teaching or student teaching (you're probably not going to be observed or be graded on how you do). Even if the class is unruly, you'll learn really quickly how to manage them. I'm quiet and shy too, and I was afraid when I first started that an unruly class would walk all over me (and they have, in the past). But, I've learned that you don't need to be loud to command the class' attention and respect. The most important thing you can do for any class is establish your classroom management routines from day one and stick with them (for example, using a bell to quiet them when the get loud, having consequences already determined for behavioral problems, having a system that rewards good behavior). If you can get some experience with classroom management before you begin student teaching, you'll be MILES ahead of other student teachers. You may be inexperienced now, but Sunday School seems like a really good way of easing into teaching without too much responsibility or stress.