Last Friday, the California Second District Court of Appeals ruled in favor of the LA teachers' union and voided a settlement that buffers high-poverty schools in LA Unified School District from layoffs. The settlement remains in effect pending ACLU's appeal to the state's Supreme Court.

Here are some things to keep in mind about this case, which has big implications for the state's law mandating reverse-seniority layoffs ("LIFO") and for the overall effectiveness of LAUSD's teachers:

• What triggered the suit that led to the settlement was the devastating impact budget-induced layoffs had on three of LAUSD's poorest schools. In 2009, these schools let go of more than half their teachers and had to bring on substitutes to teach classes. Schools in more affluent neighborhoods went largely unscathed that year.

• The LA teacher contract magnified the impact of reverse-seniority layoffs on high-poverty schools. Its provisions mandate that the order in which teachers are let go is set district-wide and not by school, as state law allows. In 2009, LA's poorest schools tended to have significantly more inexperienced teachers than average, which meant that they had to absorb the biggest share of layoffs.

• Ironically enough, by 2011 the two rounds of large-scale layoffs had already taken such a toll that the quartile of schools with the highest poverty had a relatively low percentage of first- and second-year teachers -- slightly lower even than schools in the top quartile of family income.

• The settlement completely exempted 45 of the highest poverty schools from layoffs. But another 153 schools in the lowest quartile of family income were not given blanket immunity.

• The settlement ensured that no school could be hit with more layoffs than average for the district.

• An EdTrust-West analysis of LAUSD's layoffs in 2009 and 2010 showed that there was very little overlap between the teachers who actually were laid off and those who would have been laid off in reverse order of effectiveness. In 2009, for example, the typical teacher who would have been laid off in this hypothetical model got the equivalent of five fewer months of instructional gains for her students in math than the average teacher in the district.