Exaggerating the evidence on class size

April 11, 2014

On Wednesday, Superintendent of Public Instruction Randy Dorn announced support for the teacher union's new class size reduction initiative, I-1351. The union hopes to gather enough signatures to put this initiative before the voters this November. Superintendent Dorn said:

“Reducing class sizes is key to improving student learning, particularly with at-risk students. That, in turn, will improve graduation rates.” 

This statement is unsupported by the research evidence on class sizes.

Initiative 1351 would require the reduction of class sizes to 17 students in grades K-3, but only directs the legislature to do what it does best---weigh spending priorities among competing claims for state revenue. The revenue required to reduce class sizes to this level would be $1.38 billion in 2015-17 and $3.4 billion in 2017-19. (See fiscal note to 2014 bill on class sizes, HB 2589.)

This class size idea is not new to the Washington state legislature.  In 2000, voters passed a class size reduction initiative, Initiative 728. Between 2001 and 2009, the legislature funded this initiative by providing $2.49 billion which districts used to reduce class sizes, and to offer after-school and other programs. The legislature cancelled the initiative during the recession in 2009.

Then in 2009, the legislature passed HB 2261, the school spending plan with staffing formulas requiring class size reductions like those in Initiative 1351.

Six legislatures have now decided that other spending priorities are more pressing than reducing class sizes. After all, the average class size in Washington is now at 24 in elementary schools and 30 in secondary schools, significantly lower than in the past.

Perhaps the legislature recognizes the benefits of class size reduction have been exaggerated.  In 2006, the Washington Learns commission hired two professors, Picus and Odden, from USC and University of Wisconsin, respectively. It is their prototype school model which was adopted in HB 2261. 

The research of professors Picus and Odden, however, has been severely criticized for exaggerating the benefits of lower class size and for ignoring research showing no benefits. Professor Hanushek, the highly regarded education researcher at Stanford’s Hoover Institution, says the student learning gains (effect sizes) that Picus and Odden have promised are so exaggerated that they are the “stuff of science fiction novels, not research-based school policies.”

Professor Hanushek says Picus and Odden’s method is to find a study showing a particular intervention had a certain effect on a particular group of students, ignore all other studies showing a small or no benefit from the intervention, interpret the study as showing a causal relationship, not just a correlation or association, and then assume that the conditions that produced the very large effect can be perfectly replicated throughout the state of Washington. Professor Hanushek warns Washington’s policymakers: “But pity the poor states that actually implement the Picus and Odden plan. They are sure to be disappointed by the results, and most taxpayers (those who do not work for the schools) will be noticeably poorer.”

Fortunately, some local journalists are now digging into what the research actually shows on class sizes. This week on KUOW (NPR), Steve Scher interviewed a real expert, Matthew Chingos of the Brookings Institute.  Mr. Chingos said there are many studies on class sizes, but only a few very high-quality studies, and these studies show mixed results. The one famous study showing positive gains, the STAR Tennessee study, is from the 1980’s. This was a study of 80 schools from long ago, and Mr. Chingos said it is hard to extrapolate the meaning of its findings to the modern day and across an entire state.  

Mr. Chingos said California’s experience in the late 1990’s in reducing class sizes by 10, to 20 students in the lower grades, had detrimental results when schools were forced to hire unqualified teachers. Mr. Chingos studied Florida’s class size reduction effort, and found no improvement in student learning. These class size reduction efforts have cost billions and billions of dollars. Mr. Chingos suggests that when sums of this kind are involved, it is appropriate to think about other, better uses for the money, such as paying teachers more to provide additional hours of instruction, longer school years, summer school for disadvantaged students, and other programs that could provide higher benefits to students than lower class sizes.    

This shows there is no consensus in the research that reducing class sizes would be good for Washington state. 

Research from Eric Hanushek shows that, compared to having an effective teacher, class size effects are small. A strong teacher can deliver a year more of learning to students than a weak teacher. Improving teacher quality would be a far more cost-effective strategy than reducing class sizes, and much better for students.