I think America's teachers should be paid more in money and prestige, that the discretion of principals is a better way to determine relative compensation than test scores, seniority, or masters degrees, that programs like Teach for America demonstrate the need for reform in the credentialing process, and that a necessary tradeoff as teachers are paid more in a merit based system is less job security.Teachers are educated professionals. They should be compensated like professionals. And they should be managed like professionals; not like factory workers or fruit pickers or fry cooks. As professionals, their work product is one which is complex and difficult to evaluate, and a fair evaluation of such takes time. Simple metrics such as test scores are not likely to produce fair evaluations of teachers, any more than simple metrics like lines of code delivered or defect rate are not a good basis to evaluate computer programmers (my profession). These things are important factors to consider, but are only part of the story. And metrics which are too heavily relied on are often easily manipulated; "teaching to the test" is a well-known example of this. (That said, much teaching-to-the-test is done at the behest of principals and administrators; not individual classroom teachers).
For private-sector salaried professionals (those who have a boss; not those in private practice), evaluation of the performance of professionals is the job of managers (in the educational context, principals). A key part of the job of my boss is knowing whether or not I and my peers are doing a good job, identifying things that might need improvement, and making it happen. The tools he has at his disposal include the usual artifacts of supervisory authority--the ability to assign and delegate work, to arrange for training, to manage pay, to promote/demote, and to hire and fire.
Yet many in the educational profession react with horror at the though of giving principals greater discretion to promote/demote, manage pay, and fire easily. The stated reason: concern that a principal might abuse his/her professional discretion to discipline someone "unfairly"--for reasons unrelated to job performance. Is this a legitimate concern? Yes. Yet the private sector manages to cope with this--unfair bosses exist in the private sector, and life goes on. I've had a few--and I've seen more than one talented engineer drummed out of a job due to a personality conflict with the boss. However, these talented engineers had no trouble finding work elsewhere. And legal protections against employment discrimination and harassment (and the remedies available thereunder) ought to apply with full force to teachers under any management regimen.
Teachers ought to understand this better than most people since every week they read student assignments and use their fallible judgment to assign a letter grade, often based on opaque, somewhat arbitrary standards. This process culminates in a report card sent home at the end of every semester. It typically assesses achievement on an A to F scale that presumably doesn't capture every nuance of student mastery over a subject. High school teachers who give out these grades do so knowing that for many students they'll one day be scrutinized by college admissions officers, who'll admit or deny applicants largely based on the average of these somewhat arbitrary grades that don't capture every nuance of a student's academic abilities.Evaluation of complex work products for quality is a key part of what professionals do--whether or not the work product is a technician's lab report, a paralegal's brief, a student's essay, a business's accounts, a teacher's teaching, a programmer's designs, or an executive's managerial skill. As stated above, teachers are professionals. So we trust them with the responsibility.
However, and this is important--principals are professionals too. Evaluating teachers ought to be part of their job. That said, giving principals (and superintendents) greater authority must imply that they too are held to higher standards of accountability. Just as my boss is responsible for the successful performance of the design team he supervises, and his boss is responsible for the business making money, principals and district-level administrators must be held accountable for the performance of their schools and districts.
And here, testing may be useful. An interesting management paradigm is that it's often easier to measure the performance of an organization than it is the performance of an individual within that organization; whereas test scores may exhibit too much classroom-to-classroom variation to be useful in evaluating teachers; the larger sample sizes involved make them more useful in evaluating the performance of schools or school districts.