Whenever I talk to teachers I don't usually have to wait long before they start listing their concerns about students. I wonder what would come top of your list of teachers’ complaints about student behavior. My guess is that punctuality would come pretty high. It doesn’t sound too difficult on the surface to insist that students should come on time to their lessons but in practice there may be factors that make the lateness habit difficult to break.
Take country cultures, for example. Some countries, notably those in northern Europe or North America place a high value on punctuality. To be late is considered rude, sloppy, even insulting behavior. But in other countries, punctuality is not valued in the same way. Time is seen in a much less rigid way so being a late is quite acceptable. I remember attending an appointment in the south of France for which I was dutifully a few minutes early. After I had waited for fifteen minutes, I asked the secretary what was causing the delay. She looked quite surprised and said that the person I was seeing naturally didn’t me expect to arrive punctually and expected the appointment to take place about 30 minutes after the agreed time.
Personal circumstances can also be difficult for students too. Adults coming to evening classes, for example, might find themselves delayed by work or home commitments. I once had a student who was often late because he had to have regular kidney dialysis that was scheduled to end just before his class.
I think the trick is to weigh up the situation and then work round it. If it is a problem affecting just one or two students, ask them what it is that makes them late. If they have difficult circumstances, then you have to be understanding. If it affects many class members and you feel it will be impossible to change their behavior, devise a strategy for using the first ten minutes of the lesson in a way that will mean you are not going to be interrupted in full flow as the late comers arrive.
For example, you could assign that time for homework review. Get students to work in pairs, comparing their homework and circulate among them giving a helping hand and answering questions. Once everyone has turned up to class, you can begin the lesson proper. Okay, it’s a solution that may seem defeatist but you can’t change cultural norms and you need to understand when things are tough for students. And one thing is sure. If you discuss the issue with the class and suggest this solution, then if they don’t like it, they will probably make the effort to come on time. Win-win, or what?