The problem then, is to find ways to get good teachers. This is obviously easier said than done. It is often not apparent that a bad teacher is bad until the teacher is already behind in the material. Test scores can be used to track teachers, but it requires large sample sizes, with scores taken over many years, to get anything close to a clear picture of teacher performance. The thing is, we want a way to quantify teacher success when there may not really be one. A teacher that inspires his or her students to join a science summer camp would not have a measurable change in their student test score performance. Good teachers also have intangibles, which are equally if not more important than testing performance. Not having a clear way to distinguish a good teacher from a bad one is just part of the problem of our education sector.
If a teacher is considered bad, it is not always straightforward on how to get rid of them. While some schools can certainly get rid of teachers, at others it is harder. Powerful teaching unions, along with the use of tenure, have often been barriers to the removal of bad teachers, preventing better ones from being hired.