The Los Angeles teachers union said Wednesday it is considering whether to challenge a landmark legal settlement that would end the practice of laying off educators at Los Angeles Unified based on seniority.

The proposed settlement, announced Tuesday, was reached after a group of civil-rights lawyers sued the district, claiming that budget cuts and massive teacher layoffs had created chaos for students at three inner-city middle schools. The deal still has to be approved by a judge.

A.J. Duffy, president of United Teachers Los Angeles, said he was concerned that the deal could lead to several unintended consequences, such as concentrating more inexperienced teachers at lower-performing schools.

"When the district makes a long-term policy that is detrimental to students we are obligated to challenge tha