The California teachers\u2019 union is calling for a boycott of the L.A. Times<\/em> for publishing an expose of teacher performance.\u00a0 Here are some of its findings:<\/p>\n \u2022 Highly effective teachers routinely propel students from below grade level to advanced in a single year. There is a substantial gap at year\u2019s end between students whose teachers were in the top 10% in effectiveness and the bottom 10%. The fortunate students ranked 17 percentile points higher in English and 25 points higher in math.<\/p>\n \u2022 Some students landed in the classrooms of the poorest-performing instructors year after year \u2014 a potentially devastating setback that the district could have avoided. Over the period analyzed, more than 8,000 students got such a math or English teacher at least twice in a row.<\/p>\n \u2022 Contrary to popular belief, the best teachers were not concentrated in schools in the most affluent neighborhoods, nor were the weakest instructors bunched in poor areas. Rather, these teachers were scattered throughout the district. The quality of instruction typically varied far more within a school than between schools.<\/p>\n