I have taught at more than one high school and am familiar with others which rank their senior class using a method that makes me cringe at the errors that are produced. In both math and science courses we teach the importance of using significant digits in calculating results. In establishing a numerical grade teachers normally round a student’s grade to the nearest whole number. After this is done it becomes an eyebrow lifting display of foolishness when the class ranking is calculated to four decimal places. I have shown a simplified version of what can happen in the attached document. Ann gets a higher rank than Barbara even though Barbara has actually earned higher numbers. Of course this notion of ranking a senior class is in itself a long walk off a short dock since students do not usually have exactly the same courses and the same teachers. Click below on ValSigFig to see how Ann and Barbara rank.