I think many of us have heard this statement from colleagues over the years and I hope it drives you as batty as it drives me. For all of the teachers out there that refuse to update their lessons because they seem to "work", I have this to say, "It's not about you".
I have many lessons that have worked well and others that have worked great. However, I'm constantly changing, updating or tweaking my lessons because I believe that I need to be preparing students, not for today, but for tomorrow. My lessons need to reflect the skill sets my students will need years from now in college and in the job market. They do not need the exact same skills I was trained in when I was in high school and not the exact same skills I was using with my students 10, or even 5, years ago.
One of the most time consuming aspects of my teaching career of late has been reflection. I think it is also the most valuable thing I spend my time on during the school year. I look at lessons after they are completed and decide whether or not the lesson itself is still meeting the goals and if the tools I use are still relevant to me and the students. If I do not like the answers I get from my reflection, it is back to the drawing board. This might be a tweak or a complete overhaul. I never know until I dive back into the lesson and move things around.
While this can be a time consuming part of my year, I can feel assured that my lessons are always the best lessons I am offering my students that year and the next.
Just because a lesson "works" does not mean it is the best lesson for that topic. Their are many lessons that can "work" just fine, but there are others out there that could have a great and longer lasting impact on the students if the time is taken to review them and look for alternatives. We all want lessons that are great for our kids and are not too time consuming on the teacher's end. Some of the best things we do as educators takes time and lesson planning and reflection is no different.
As you go through your school year, please take the time and look at your lessons and ask whether or not this is the best lesson for this topic. In the end, it is not about you right now, it is about the students and what they need years from now.