Spending a single year with a lower-quality teacher can cost a student tens of thousands--or even millions of dollars--in future lifetime earnings, according to research reviewed by Bloomberg BusinessWeek.

A judge recently used this research as justification for striking down parts of California's teacher tenure rules. His ruling concluded that the "near inability to fire ineffective teachers disproportionately hurts poor and minority students," the business publication reported. 

Highly ineffective teachers, the evidence suggests, can cause lasting harm that continues far into a student’s future. ”Based on a massive study, Dr. [Raj] Chetty testified that a single year in a classroom with a grossly ineffective teacher costs students $1.4 million in lifetime earnings per classroom,” Judge Treu wrote in his 16-page decision.

The 2012 study--by Harvard’s Raj Chetty and John Friedman and Columbia’s Jonah Rockoff--analyzed data from 2.5 million kids over two decades, matching test scores with tax data for the same students and their parents. 

See the judge's decision.

Read the full article.