There is a story told, probably apocryphal, about Harry S. Truman. Upon hearing from an aide that 50 percent of Americans possessed below-average intelligence, the president was reportedly shocked and dismayed. Same thing happened last week in the Florida Legislature when, by request of House Education K-12 Committee Chairman Bill Andrews (R-Delray Beach), education officials reported that more than one-third of Florida's high school students were carrying less than a 2.0, or C, grade point average. Andrews ordered the study as a tool to help identify poorly performing school districts. He figured, using Trumanesque logic, that any district with less than 75 percent of its students earning above average grades is in trouble. "We thought that might affect four or five districts, but we have 61," he said. "If these numbers are correct, that's a crisis of emergency proportions," said Rep. Debbie Wasserman Schultz (D-Davie). Actually, it is a crisis: last Wednesday, Gov. Lawton Chiles decreed that all children must achieve a C grade to graduate. But it is also a joke. Hey, Einsteins: the definition of average is, like, common or something. Orange County doesn't believe it. Last year Chiles vetoed a state plan to raise the numerical score required to earn a C from 70 to 77 points, Orange County adopted the grading scale anyway. Now a B is 85-93; and A is 93 or above; 76 gets you a D, and a 69 earns you an F. The grade point average is calculated using the letter grade; an A earns students 4 points, B equals 3 and so on. Until last year a Florida kid needed a 1.5 to get the diploma. That's a D-plus, and it would plot on the bell curve about half a standard deviation below average. The new law requires a 2.0, top dead center of the bell curve, meaning that no one in Florida who has below average grades may graduate. In Orange, the rule will require for graduation nearly what used to be a B. April Podnar, spokeswoman for Orange County Schools, says the move toward tougher grading is part of an overall plan to improve education. So is a C still average? To what degree will teachers simply award the higher grades needed to graduate to the numbers of students large enough to get them through the rickety cash-strapped system? "I don't follow," Podnar demurs. Here is our thinking: The grade crisis is reminiscent of a scene in the movie "Bananas" in which Woody Allen, as director of the tropical paradise, announces solemnly that, "All children under the age of 16 are now 16."