In Michigan, 98 percent of teachers were rated effective or better under new teacher-evaluation systems recently put in place. In Florida, 97 percent of teachers were deemed effective or better. Principals in Tennessee judged 98 percent of teachers to be "at expectations" or better last school year, while evaluators in Georgia gave good…

Hillsborough County (Fla.) Public Schools had a concern. A review in 2008 of teacher evaluations in the district found that more than 99% of the 12,000 teachers were rated satisfactory or outstanding, and nearly half of high school teachers received perfect scores. While Hillsborough is a high-performing district and has several high schools on…