Someone once said to me that good teachers should be planned ahead two weeks at a time.
I'm not sure why that sticks in my head, but while I think I agree in theory, I'm not sure it actually makes sense to follow that to the letter.
Here's an example. In our school, the First Grade team has developed a set of Yearly Plans. Our Social Studies/Science plan is a bit more comprehensive than the Language Arts one, and really, they are all just works in progress. With Math, we've been following our Math curriculum (for some, Silver Burdett-Ginn. For me, Investigations), so the Math yearly plan was almost empty.
Well, this year, our school system has mandated that all teachers follow the Mathematics Pacing Guide that they've created, which pulls Standards of Learning from the State's website and blocks them out into the various quarters of the school year. (My objection to the way they've blocked some of them out, ie, focusing on counting only in the first quarter and no combining or separating, is a discussion for another time)
So, this year, I've been using the Investigations curriculum, but far less than I'm used to. With a focus on counting (by 1's, 2's, 5's, 10's), number recognition, and etc... I've been inventing a lot of the work that my students are doing [example here, though pictures are missing. :( ].
Yes, I'm planning 1-2 weeks in advance... but every week what I plan changes. I may say that I'm going to do a particular investigation into counting by 5's on a certain day, but it changes based on what I'm seeing the children do (both in what they are capable of and that with which they need more practice).
Isn't that the point, really? To plan ahead, but to tweak and change and throw out entirely lessons that are not appropriate, and instead work with the children where they are, not where I thought we'd be two weeks ago...