Developing an equitable tardiness/attendance system

How do you compare two student employees who have different tardiness and attendance issues? It's not easy. Some student employees have issues with tardiness, some have issues with attendance, and some have issues with both tardiness and attendance. In an effort to make sure that disciplining employees for such issues is equitable, we developed a point system. Points are assigned to various tardiness and attendance issues, and in a semester, student employees are allowed to accrue no more than 12 points. We developed this point system in conjunction with our student employees to ensure their "buy in" with the assignment of points for various tardiness/attendance issues. It has worked well for us, and to continually improve this point system it has evolved and will likely continue to evolve.