In a subject like the one I teach, most, if not all, of our students have some outside commitments. If it's not work, it's children, or other family, who need looking after. Sometimes it's both. This, naturally, means that in some cases, attendance can be rather sporadic.

However, it still seems to obey Murphy's Law. Just because a student hasn't turned up all week does NOT mean they won't turn up to your lesson. And they are most likely to do this when you've planned (and made resources) for the class without them there.

Conversely, you can't guarantee that a particular student will be in your lesson. You have to plan for all the students being in class, but allow for some of them being absent.

It's a barrier to learning, and it's also a possible problem. It is, therefore, something I need to start including in my lesson plans, because student absence or attendance still throws me from time to time.

What's irritating is the waste of resources when the former is the unexpected event.