Last year one-half of one percent of Michigan's public schoolteachers were considered to be “ineffective” according to performance evaluations conducted by the nearly 900 charter and conventional school districts in the state. Those assessments appear at odds with the actual academic performance of students, and teacher evaluations have become problematic in other ways since a state law was passed in 2011 mandating more teacher accountability. Of the 95,885 teachers evaluated, just 519 earned the lowest rating of “ineffective.” Under that 2011 law, a teacher rated “ineffective” three years in a row can be fired. The law also requires teachers' performance...