Lack of Content Knowledge
Most states require teachers to pass a comprehensive series of assessments to obtain certification within a specific subject area. With this requirement, you would think that all teachers would be proficient enough to teach the subject area(s) they were hired to teach. Unfortunately there are some teachers that do not know the content knowledge well enough to teach it. This is an area that could be overcome through preparation. All teachers should thoroughly go through any lesson before they teach it to make sure they understand what they are going to be teaching. Teachers will lose credibility with their students extremely fast if they do not know what they are teaching, thus making them ineffective.