A new study shows Portland is among the areas of the nation ranked highest in teacher absences.  The study, conducted by the National Council on Teacher Quality, shows Portland teachers miss 14 school days per year on average.  "USA Today" reports the figure doesn't account for serious, long-term illnesses or pregnancies, but does include training days.  According to the study, Portland has more than 600 teachers who miss more than 18 days per school year.