MARTHA MAcCALLUM, KELLY McKENNA: America's next 250 years begin on the playground

As we enter the "dog days" of summer in this 250th, since our nation boldly asserted its independence, there is, as there should be, a good deal of reflection about who we are, what we truly value. As we look to the future there is perhaps no more important measure than how we educate our children so that they can be strong protectors of our country and our democracy deep into the decades to come. It turns out that a basic truth of well-being, getting fresh air and play time, plays a pretty big