The quotation by Bransford, Brown and Cocking in How People Learn, which speaks to expert teachers having a firm understanding of their discipline, is quite poignant. When teachers instruct outside of their areas of expertise, it results in ineffectively educating their students. They lack the pedagogical content knowledge and are unable to support the questions that students ask. On the other hand as stated, being an expert in your discipline does not automatically translate into the possession of effective teaching skills.
In one of the other readings it stated that future science teachers are not prepared with the pedagogical and science content knowledge required to go in dept. It further states that on the job, science teachers have few chances for improvement with professional development opportunities limited in quantity, availability and scope.