Hi Jun!
1st, a lesson plan doesn't necessarily have to be a physical thing; i.e. a piece of paper - although in a classroom, it always is. In freestanding situations such as the dojo, a lesson plan can be carried in the head. In other words, it is a mental map of your class for the day that keeps you on track, just as I described in the text. To elaborate, the primary importance of a lesson plan is to organize an instructor's thoughts and materiel into an efficient sequence for your students to learn from. So long as the instructor knows how to set up a good LP, the actual physical piece of paper is not required. Although it must be said; it can help enormously if you sit down and write one up before class, no matter how good a teacher you are. I do whenever possible, even if its a class I've taught dozens of times before.
As for 'scrapping' a lesson plan; sure, I have from time to time, when circumstances warrant. The thing to remember is; if you decide to skip a LP and go with a different topic, make sure you - the instructor - are doing it for your reasons; not those of the students. What I mean by that is this: Let's say you're planning to teach Taigi #1. During the warmup, you realize that one or two students (or more) are so hurtin' at Tenkan, it would be better to concentrate on the basics of tenkan itself, rather than the taigi. That's good; you're abandoning your prepared work in favour of something more important. If, on the other hand, you announce 'We're going to work on Taigi #1 today..." and you get a chorus of groans and expressions of boredom ("Awww, Sensei; we took that Friday!"); then it may be best for you to persevere; you ARE the instructor after all. ("We did? Good, then you should know all about it. OK, first two...")
The whole point of an LP is not to bind you into one subject for the day of course; it's there as a teaching aid; a mental organizer. As such, while I said - and still say - 'You can't teach without a lesson plan', I should elaborate it by saying 'You can't teach to your maximum effectiveness without a lesson plan.'
Thanx for the question, Jun; hope this helps!
Dave
(BTW - Remember, everything I put into that document are my own opinions based on my teaching experience. Teaching is an art, so there may be many, many different interpretations on what's "right". This one's mine.
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