(paraphrased) WASHINGTON--It took awhile for the class to warm up to him, but former Washington Mayor and convicted felon Marion Barry quickly had about 15 Ballou High School students talking about chemistry. At a school in one of the District's roughest neighborhoods, Barry taught a lesson and called on sleepy-eyed students, pressing them for answers about chemistry. "One thing you always got to do is speak up," Barry told the class. "Be careful of the people that you steps on the way up," he said. "because sometime you'll meets them on the way down!"Besides taqlking chemistry, Barry, 68, told the...