Principals use classroom observation forms to evaluate a teacher's performance and adherence to teaching standards for her district. These forms can be short, for informal observations, or longer and more involved, for formal observations.
Not all districts require the use of specific forms for teacher observations, but most principals use forms to record their observations during a walk-through. Principals then use these notes to help their staff reflect on areas for growth and areas of strength, as well as score them if their districts use a formalized teaching rubric. EducationWorld.com has compiled many forms and rubrics that principals use for teacher evaluation.