Introduction Think back to the last time a student surprised you with a poor result. The student was present, polite, and seemed to be keeping up. Then the exam came, and the marks told a different story. Looking at the records afterwards, the clues were all there: homework handed in a day late, then two days late, and quiz scores edging down a few marks at a time. Nothing was missed out of carelessness. A busy term simply leaves little room to compare one week with the next. This is wher...