It's a bit more complicated:
"The plan would most likely mean teacher layoffs in middle-class areas that are accustomed to having the same teachers come back year after year. So while Sonia Miller, the principal at Gompers, will have less turmoil this year, the churn will be passed on elsewhere."
First thing to say: It's fucking stupid to lay off any teachers at all. We should be hiring more. Note, though, the institutional classism of the seniority system: if the primary criterion of layoffs continues to be seniority, middle class families will benefit, and poorer families will get screwed over, as usual. Carrol will probably hates this, but I think it's irrefutable: seniority preferences for public school teachers reinforce the class system by providing stable education in affluent areas and encouraging "churn" in poor areas.
Miles