There should be no or little room for professional growth for teachers. If you teach 2nd grade this year and do your job, what professional growth do you need to teach next year? This is no different than doing a job any where else whether you are running a deep fryer at McDonalds or an accountant in a business. That is as long as you are doing the same job next year. Note about accountants and other professionals: education is required to keep up with current practices. I contend that teaching 2nd grade should have been perfected by now, and there are not changes to current practices.
I home schooled my daughter during their elementary school years. 2nd grade was not difficult to teach and I do not have an education degree. My youngest daughter went to cyber school last year. She had AP calculus. Calculus has not changed since I was in college, other than a decline in the quality of the textbook. My daughter completed her calc with a grade of 98%. That was achieved by breaking out my college textbooks, problem solvers and a little tutoring on my part. The point about calculus is calculus has not changed and teaching it doesn't need to change. Basically, all of education can remain the same through high school with the exception of history, which needs to be updated with the passage of time.
So does professional growth mean preparing to be an administrator? That is a career change in my book and in most businesses you pay for your own education for a career change.
The real problem with education today is that a bunch of weak-minded liberals, that are often functionally illiterate, are running schools. They lack all ability to decompose educational material into learnable pieces of information. Then they overly complicate the education materials with a bunch of liberal mumbo-jumbo. When home schooling my daughter their school year was divided into 20 to 26 lessons for most subjects, particularly math. Sometimes a lesson would take two weeks to master and sometimes a morning. We moved on to the next lesson once the prior lesson was mastered. Then we moved on to the next grade in the middle of the school year. Bottom line, teaching isn't close to rocket science. It is closer to running that deep fryer at McDonalds.
Degrees in relevant subject areas are highly prized by top public schools. A friends daughter had an MA in education and an MA in math, and the offers she got right away were very good. After a few years experience, she easily topped $100K for a school year. These kinds of pubic schools want large numbers of their kids to get the top grade on the calculus AP exam, and are prepared to pay to insure that this happens. If you are really good, all the richest towns will want you.