Although free breakfast is available to all students in Miami-Dade Public Schools, only a small fraction are taking advantage of it. Even a registered dietitian with a master's of science degree and oversight of food services in the nation's fourth-largest school system, Penny Parham, advises: Breakfast is the most important meal of the day. ''I sound like an old grandmother, but nutritionally, it's the truth,'' Parham said. ``Everybody should eat breakfast -- hands down. Research is clear and strong.'' Free breakfast has been available to all Miami-Dade students for more than a year, but Parham said participation is still low....