. >> reporter: fourth grade teacher kelly iwamoto of inglewood, california, says she knows firsthand how precarious her job can be. because she doesn't have enough seniority, she's been laid off three times in the last three years, then brought back. even so, she supports the seniority-based layoff system. she says it's objective and clear. >> it's fair. it's fair, and i support it. >> reporter: iwamoto also says she supports the other part of the law that's being challenged: permanent status for teachers after two years. she says that provision actually helps her advocate for students without fear of being fired. >> because i speak out very frequently about resources being brought to our district for and if i'm vocal and someone doesn't like what i'm saying, then i can be let go for that. and i don't think that's fair. >> reporter: iwamoto and the unions also say a teacher's "effectiveness" is difficult to measure, and, they say, students don't necessarily connect with every teacher. during the trial, elizabeth vergara testified that she learned nothing in english class and wasn't a