Tuesday, August 17, 2010

Measuring teachers

Sunday's LA Times had another big article on Sunday, telling which 5th grade teachers in the LA Unified School District are good and bad, with names and pictures of a couple of the best and worst.

The Times got LAUSD to give them 7 years of math and English test scores and gave them to a moonlighting researcher from the Rand Corporation, who applied a statistical approach called value-added analysis.

They looked at test scores as percentiles, to control for home-life issues. If a kid scored int he 30th percentile because his mom is single, poor, and uneducated, so he got to kindergarten knowing half as many words as the other kids, he's probably going to score in the 30th percentile next year, too, unless he has a particularly good or particularly bad teacher.

The Times found that in some teachers' classrooms in the same school (which controls for neighborhood and local events), kids consistently raised their percentiles, and in others, kids consistently lowered them. Kids got better or worse compared with the other kids. The difference is attributed to teacher quality.

This has good and bad aspects to it. I think the methodology is nicely done. It's similar to an idea I had, but much simpler and cheaper. I've written before why and  how I thought we should measure teachers. And we already knew from a twin study and other research that some teachers are better than others at teaching reading.

This analysis I think accurately tells which teachers are good at having their kids score well on California's standardized 5th grade tests. To the extent that scoring well on those tests measures the quality of a kid's education, the analysis is valid to measure teachers. The Times' experts said they thought it should account for  a fraction of the measurement. (I forget what fraction they said, and the newspaper is all the way in the living room, and I can't find it in the online version. If I find it, I'll insert it, delete this sentence, and pretend I knew it all along.)

But you know that the cheap, easy, incomplete measure will become the sole standard in practice. And teachers will have even more incentive to teach to the test.

One thing I wonder about. Perry Preschool's educational advantage was all in girls. Boys showed improvement in not receiving social services as an adult, not being arrested, and owning their own home at age 27, but income and educational advantages were pretty much all for girls. So I wonder how the LA Times analysis would look if you separated girls from boys. And if you looked at boys arrest records after 10 years.

And so to work, with images of failing teachers and lost kids in my head.

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