“Perhaps just as important, given the difficulty of finding, training and retaining outstanding teachers, is that the difference in long-term outcome between students who have average teachers and those with poor-performing ones is as significant as the difference between those who have excellent teachers and those with average ones, the study found. In the aggregate, these differences are potentially enormous. Replacing a poor teacher with an average one would raise a single classroom’s lifetime earnings by about $266,000, the economists estimate. Multiply that by a career’s worth of classrooms. “If you leave a low value-added teacher in your school for 10 years, rather than replacing him with an average teacher, you are hypothetically talking about $2.5 million in lost income,” said Professor Friedman, one of the coauthors.” #образование - × × ×

“But controlling for numerous factors, including students’ backgrounds, the researchers found that the value-added scores consistently identified some teachers as better than others, even if individual teachers’ value-added scores varied from year to year. ¶ After identifying excellent, average and poor teachers, the economists then set out to look at their students over the long term, analyzing information on earnings, college matriculation rates, the age they had children, and where they ended up living. ¶ The results were striking. Looking only at test scores, previous studies had shown, the effect of a good teacher mostly fades after three or four years. But the broader view showed that the students still benefit for years to come.” - × × ×