Lesson plans ensure that you keep your class moving on track, reaching specific goals during the semester. This also allows you to make changes during the semester when you realize that your class is getting off track. For instance, you can look at your lesson plans every evening, compare them to the lesson you presented that day and realize immediately if your class is falling behind. You can then choose to omit other lessons, shorten other lessons, or combine two later lessons in order to catch your class up to your lesson plans.
Students can help you save time by knowing what to expect each day and preparing for your lesson ahead of time. This includes bringing the things to class they will need and doing any necessary reading before your actual class meeting. Make a copy of your lesson plans that includes your students' responsibilities for each class and the materials they will need to bring on that day. Pass these out to your students and make sure they know to come to class prepared. This saves you time, allowing you to move directly into your lesson instead of repeatedly reminding your students about upcoming responsibilities.
As a teacher, you cannot avoid the fact that you will have to miss school at times. You may become ill, have a family emergency or have other responsibilities that pull you away from your class. In these cases, a complete lesson plan allows your substitute to lead your class in the daily work, avoiding wasted days and wasted time from absences. You can prepare worksheets and educational displays ahead of time, and rely on your substitute to present these to your class and keep students moving on your schedule.
During the semester, you can make notes on your lesson plans about particular problems, such as lessons that required additional days or projects that were unsuccessful. At the end of every semester, you can recycle your lesson plans by reviewing your notes and adding additional time for projects that took too long and replacing projects that were unsuccessful. This saves you from having to begin new lesson plans every semester, allowing you to make simple revisions instead.