Dana Goldstein said:

[Teacher tenure policies] aren’t the only, or even the primary, driver of the teacher-quality gap between … middle-class and low-income schools. The larger problem is that too few of the best teachers are willing to work long-term in the country’s most racially isolated and poorest neighborhoods. There are lots of reasons why, ranging from plain old racism and classism to the higher principal turnover that turns poor schools into chaotic workplaces that mature teachers avoid. The schools with the most poverty are also more likely to focus on standardized test prep, which teachers dislike. Plus, teachers tend to live in middle-class neighborhoods and may not want a long commute.

Educational equality is about more than teacher-seniority rules: It is about making the schools that serve poor children more attractive places for the smartest, most ambitious people to spend their careers. To do that, those schools need excellent, stable principals who inspire confidence in great teachers. They need rich curricula that stimulate both adults and children. And ideally, their student bodies should be more socioeconomically integrated so schools are less overwhelmed by the social challenges of poverty. Of course, all that is a tall policy order; much more difficult, it turns out, than overturning tenure laws.

via http://www.theatlantic.com/education/archive/2014/06/california-rules-teacher-tenure-laws-unconstitutional/372536