ED Kain has been blogging a lot about teacher firings, and makes what I think is one of the better cases for the tenure/civil service/union protections from firing that teachers now enjoy.
Teachers need protection from over-zealous bosses and ideological politicians. This is the same thinking behind seniority rules, which protect more expensive teachers (i.e. veterans) from being laid off due to budget cuts. Teaching is not a high-paying job compared to jobs in the private sector, and one of the benefits is some job security. Occasionally this means bad teachers take longer to fire.
But the answer to that problem is not making all teachers easier to fire. This would undermine teacher recruitment. If you take away pensions, job security, tenure, the ability to unionize, and basically all the other perks of teaching, what you’re left with is a very difficult job with no job security, mediocre benefits, and relatively low pay. This is not how you attract good people to a profession, or how you guarantee a good education experience for your children. Paying starting teachers more but making their long-term prospects in the career less certain is also wrong-headed. High turnover is not desirable for any business, teaching included.