Experience as a Liability

"The more experience you have, the more marketable and valuable you become".  This seems intuitive and is true in many careers, but not in teaching.  There is considerable disagreement about the degree of effect that experience and credentials have on teacher quality.  Years of experience and credentials (i.e., degrees) are really the only proxies currently available for assessing the "quality" of teachers.  Granted there are numerous evaluation systems currently in use (such as Danielson's Four Domains of Teacher Responsibility), however these systems are still a ways off from being actively applied to rank and measure teachers.  There is considerable evidence that supports the claim that after five years, teacher quality plateaus (though there is a measurable "vintage" effect that arises around 25 years of experience).  Furthermore, a vast body of research indicates that Master's degrees have practically no impact on teacher quality and student achievement, except for math and science teachers and then only when the degrees earned were in those specific subject areas.  Though there are inherent weaknesses in the measurement of teacher quality, it is the system in place and must do until something better replaces it.  Teacher quality varies considerably, with most teachers being "average", but teachers in their first five years of teaching vary the most.  It is obvious that first year teachers, regardless of their overall "quality", will likely have lower impacts on student achievement than a teacher with more than five years of experience.  At this time there is not much available to school leaders to accurately predict the future success of a teacher except maybe by using standardized test scores (SAT, GRE, PRAXIS, etc.), college grades, and a few other proxies.  Therefore, one could not effectively determine the differences in future success of a teacher fresh out of a preparation program and a teacher with several years of experience.  Yet many schools are hiring teachers with only a few years experience or no experience OVER teachers with several years of experience.  How can this be?  The simple answer is that it comes down to money.  It is vastly more expensive to hire a teacher that has ten years of experience and a Master's degree over a student intern with no experience and a bachelor's degree.  For instance, the cost "savings" in one district would be $20,840 if they hired a teacher with a BA and no experience over a teacher with a Master's degree and ten years of experience.  From a fiscal perspective this seems to make sense, but one must also consider the longitudinal ramifications.  Since it is extremely difficult to gauge the impact on student achievement of the new teacher, it is a total gamble.  With the experienced teacher, there is usable "data" (letters of reference, and the "signal" of experience and credentials) to use in the hiring process.  It is troubling that experience has essentially become a liability to teachers and clearly minimizes their mobility between schools and districts.  Obviously this is not always the case, but seems to be a rising trend.  Teacher turnover is a negative externality that drastically impacts schools across the country, but teachers shouldn't be stifled in their ability to change locales.  School budgets are tight and given that teacher salaries and benefits make up the greatest portion of budgets, school leaders may be "forced" to make cuts by hiring inexperienced teachers.  I should be clear that I am NOT saying that new teachers should not be provided a chance or that they are somehow less able than experienced teachers.  Often, teachers with no experience may very likely be more effective than a teacher with 5, 10 or 20 years of experience.  The problem is when experienced teachers are passed over because they are too expensive to hire.  This is an issue than requires further research to validate and practical solutions for school leaders to utilize.