Recent HS grads not being filtered out


We've run into a strange issue where some high school students who just recently graduated are able to check in. On many occurrence types, we do not have an age range set, it's determined by grade only. Once a person has graduated from high school, the grade calculation done returns -1, instead of 0-12. In some fringe cases, it seems that we're allowing people to check in that otherwise shouldn't be able to.
Corrected in CheckInBLL.cs Revision 44