State Departments of Education Should Stop Trying to Predict Who Will Be a Good Teacher

Teacher quality is hugely important. The difference between a good teacher and a bad teacher can be as much as a year’s worth of learning. These academic gains translate to increased earning potential for students with great teachers.  In his paper, “The economic value of higher teacher quality,” economist Eric Hanushek writes, “A teacher one standard deviation above the mean effectiveness annually generates marginal gains of over $400,000 in present value of student future earnings with a class size of 20 and proportionately higher with larger class sizes.” So, when the Missouri Department of Elementary and Secondary Education (DESE) decided to focus on teacher quality in the “Top 10 by 20” initiative, it made sense. The problem is that DESE’s efforts to improve teacher quality are completely misguided.

DESE decided the best way to improve teacher quality was to raise the bar on licensure exams. Licensure exams and other certification requirements are only effective at improving the quality of the workforce if they are related to the outcome we desire; namely, increased teacher quality. The figure below offers an illustration. This figure comes from a paper by economist Dan Goldhaber, “Everyone’s doing it, but what does teacher testing tell us about teacher effectiveness.”

On one axis, you have a measure of teacher quality and on the other a teacher’s performance on licensure exams. The height represents the number of teachers, with most being somewhere in the middle. The red line indicates a minimum passing score on the licensure exam and the blue line indicates some minimum level of teacher quality. If teacher quality and performance are highly related, as they are on the left figure, then a licensure exam could do a good job of screening out individuals. “A” represents the individuals who would be good teachers, but are kept out because they fail the test, “B” are the bad teachers who fail the test, “C” are the bad teachers who pass the test, and “D” are the individuals who pass the test and are adequate teachers. As you can see, when the test isn’t related to teacher quality, as presented on the right, we have more ineffective teachers passing the test (“C”) and more good teachers failing the test “A”.

Teacher licensure tests are more like the figure on the right. They do a poor job of predicting who will be a quality teacher. What DESE did is move the red line further to the right; thus, keeping more people out.

The fact is, we are lousy at predicting who will be a good teacher. Thus, increasing the rigor of licensure exams will not do any good. Hanushek offers another solution – teacher de-selection. He writes, “replacing the bottom 5–8 percent of teachers with average teachers could move the U.S. near the top of international math and science rankings with a present value of $100 trillion.” Rather than try to predict who will be a good teacher, we should focus on removing those individuals who have proven to be bad teachers.

Raising the bar on licensure exams will not improve the quality of the teaching profession. If we want to do that, we need to make teaching more attractive to high performing individuals and we need to get rid of the bad apples in the teaching profession.