As people get older, they need to begin to develop responsibility with the things that they do. Being on time for a class IMO is not showing very much responsibility. As its been said, sometimes things such as accidents, traffic jams, bad weather, etc. can lead to delays.
Now, on a different note: If the attitude is "Oh well, if I'm late, I'm late", whats going to happen when that person gets out in the real world with a job? Chances are, if they're late on a regular basis, they just might find themselves without a job.
Mike