Teacher tenure and civil rights

A California judge ruled Tuesday that teacher tenure locked so many incompetent teachers in place in poor performing schools in distressed neighborhoods that students in those schools were being deprived of their right to an education.  Prominent economists were hired as expert witnesses in the case.  Judge Treu cited the work of Harvard economist Raj Chetty who found that a single year in a classroom with an ineffective teacher costs the students $1.4m in lost lifetime earnings.  Tom Kane, another Harvard economist, testified that one year with an incompetent teacher costs 9.5 months of learning.

California teachers go up for tenure after only 16 months on the job.  Once tenured it takes 2 to 10 years to remove an ineffective teacher at a cost of $50 to $450k, the judge noted in his ruling.  With such a daunting process and a far from certain outcome, principals choose to leave such teachers in place.

So how does this become a civil rights issue?  The judge cited testimony that inept teachers tend to be clustered in "high-poverty, low-performing" schools with large concentrations of minorities.

Of course the ruling will be appealed and the next judge may weigh the testimony differently.  Looking at the economic and management issues at stake, here are some key questions:
1) The judge cited testimony from an expert witness hired by the defendants that 1-3% of all teachers in California are ineffective.  Ineffective teaching is not an easily measurable trait such as height or weight. If the ruling holds up, how would teaching effectiveness be measured and how would one use those measures to make decisions at the individual level?  In practice performance measures are always noisy, so the consequence would be that some good teachers would be fired because of bad metrics.
2) Who replaces the fired teachers?  Would the replacements be more or less effective in the classroom?
3) Would principals use the power to fire?  Dismissal procedures are not any fun for either party.
4) If tenure is removed, this reduces the economic rewards for entering the teaching profession.  How much will salaries have to be increased to attract the same caliber of faculty?
5) There are many issues facing inner city schools and their students; if every ineffective teacher were replaced by an ideal teacher (think Mr. Chips, Sidney Poitier in Blackboard Jungle, or Robin Williams in Dead Poets) how much would the lives of the students in those schools change?  The roles of neighborhoods, parents and culture would remain more or less the same.