Easy to make a blanket statement, but as always, there are exceptions. Pro, like myself uses public transportation. And I know more than once she's faced same thing I did. Get on train that's running on time, that gives you more than enough leeway to get to studio on time, wram up, etc, and still have some time before lesson, then there's an accident blocking tracks. Or in last case when it happened to me, some idiot on a bike who tried to race the express train and didn't make it.... I think I've had a group start late, due to teacher, maybe 3-4 times a year, and with good reason. Just konw that in a busier studio than mine, those same valid reasons, might happen more often. But of course most important thing is that when it does happen, with my situations, with reasons for the case, and the people involved, we don't have a problem with it. Are always individual personalities involved, and relationships between them, so something that is alright in one teacher/students relationship might not be in another. And people need to be aware of this differences and work within them as best they can, particular the teacher, as this is a service oriented business.