I'm 12 years old, and a regular Slashdot reader.
I'd like to offer my opinion on this:
We don't need longer school days. We need more courses and teachers. Specifically, we need more separation of classes based on ability. To Heck with this 'fairness' stuff. We really need at least two classes: advanced and less-advanced. Sure, some kids will feel bad when they don't make Advanced, but it's worth it.
Allow me to elaborate. Longer days don't make an ounce of difference if half the kids are bored out of their skulls. All my fancy, expensive, private school has managed to do is bump me a year up in Math. And I'm still ahead of the class. In all the other classes, I'm stuck where I am. I spent half of 5th Grade correcting other kids' work for the teacher. And it's not just me. There are plenty others in the same boat as I. We don't learn much (especially on a time-to-learning scale), and longer/more days won't help.
If we separate by ability, eveyone wins (except the schools, who have to hire more teachers): The kids who are ahead have engaging and new stuff to do and learn, while the kids who aren't ahead have things tailored to their needs. And, everyone gets smaller classes and more time with the teacher.
If we're going to do anything, I suggest we, in some way or another, give kids material that is at the right level for them. Maybe once we get that done, we can think about longer school years or days.
Actually, I'm not strongly against a few extra weeks, as long as the school curriculum is challenging.
If anyone reading this has any say in this kind of thing, please think of me.
-Nathan