Kids are sometimes late to their classes.
Every day I see some kids come in slightly after the bell in almost every class. Also, having too many tardies is the leading reason why kids are stuck in detention after school. My brother has told me that he has been late to some of his classes as well.
In Tartan the circle entrances are too narrow, which causes a huge slow-down at the entrances to the circles. Also, some kids have bad scheduals in which their classes take them from one end of the building to the other, plus the stop at the locker in between. The passing times also may be a little shorter than they should.
The best solution would be to lengthen the passing time by just a minute or two. Making the circle entrances wider would also help significantly.