The Los Angeles Times crunched a bunch of numbers on standardized test performance over the last seven years to gauge the relative effectiveness of various teachers in the city. Then it published a summary of the results, noting that there is a huge gap between the gains shown by kids in classrooms with a good teacher and those right down the hall suffering under a bad teacher. Obvious, as far as it goes. Interestingly, they also found that the variation between teachers was more important than the variation between schools.
But the Los Angeles Times also promised to publish a bunch more stories based on the teacher quality data, and they say they're going to make their database public. Naturally, the union is now calling for a boycott of the paper by its 40,000 members. But here's the part that really kills:
The district has had the ability to analyze the differences among teachers for years but opted not to do so, in large part because of anticipated union resistance, The Times found.
Lots more on teachers unions here.