Few education reforms make as much sense on a gut level as giving teachers fewer students to teach.
The idea is popular with parents and politicians alike – at least 40 states have carried out some kind of class-size reduction in the past 15 years.
But, despite more than four decades of research in the U.S. and abroad, the effects of this simple idea about how to raise student achievement have been hard to isolate and measure, leading to academic squabbles over its value.
Researchers generally agree that smaller classes, at least in the earliest grades, are linked to positive educational benefits, such as better test scores, fewer dropouts and higher graduation rates, especially for disadvantaged children.
They disagree, however, on whether those benefits outweigh the costs.
In recent years, researchers have been trying to figure out why smaller class sizes work, how they work and who benefits most.
Nailing those questions would help educators, policymakers – and the public – understand what else they need to do, besides just shrinking classes, to get the biggest bang for the buck.
The studies, based on classroom observations and interviews, have revealed some surprising insights:
– The most obvious explanation for why reducing class size works – that teachers give students better, more-tailored instruction in smaller classes – probably isn’t the reason achievement goes up. Teachers for the most part don’t change their practices automatically when their classes have fewer students.
– Students behave better and pay more attention in smaller groups, and this may account at least initially for the gains. For example, it’s harder for a couple of troublemakers in the back of the room to derail the class when they can’t hide in a crowd.
– Reducing class sizes can have the potential to make a big difference for students only if teachers get the training and administrative support to take advantage of the situation by changing how they teach and how they interact with parents.
The most persuasive class-size research in the United States comes from a large experiment in Tennessee in which students in small classes outperformed students in larger groups, even when teachers had the help of aides.
Project STAR (Student Teacher Achievement Ratio) was conducted in Tennessee from 1985 to 1989, and involved more than 1,200 teachers and almost 12,000 students, according to Jeremy Finn of the University at Buffalo (State University of New York), a statistician who helped set up the experiment and publish its results.
While no study of such a complex subject is immune from criticism, the results from Project STAR are highly regarded because teachers and students were randomly assigned to classes of differing sizes.
That kind of experimental design is considered the gold standard because it gives researchers confidence that the effects they are seeing stem from the change (smaller class sizes) and not some other factor.
The Tennessee results inspired California and Wisconsin to carry out statewide class size-reduction projects in lower grades in 1996, a time when state governments were enjoying surpluses.
There’s scant research on the effects, positive or negative, of reducing class sizes in the upper grades because the variables are much harder to pin down, Finn said.
Wisconsin achieved similar results to Tennessee, but California did not, which showed that simply making classes smaller is not all that needs to be addressed.
In 2003, Finn co-authored a paper that identified a gaping hole in the puzzle:
“Despite the many studies that show positive effects, research has yet to come up with a consistent, integrated explanation for the gains attributable to reduced class size,” according to the paper, published in the journal Review of Educational Research.
The most intuitively satisfying explanation – that teachers give students more individualized instruction in smaller classrooms – didn’t pan out when researchers observed what actually happened in smaller classes.
Several studies have found that, while teachers may have more interactions with students, they tend to teach the same way they always have.
Finn and his colleagues proposed a different explanation, which they believe better fits the evidence from the studies and also jibes with classroom observations: Students behave better and participate more often when they can’t hide in the back of the classroom.
Smaller, quieter classes (fewer than 20 students) may have their biggest effect on kids who are inattentive and try to avoid looking the teacher in the eye. That’s because they can’t hide either.
Using Project STAR data, Finn compared the academic performance of fourth-graders considered to be disruptive, inattentive or neither.
“Most people I talk to predict that the disruptive kids are the worst, but they’re not. The inattentive, withdrawn kids are by far and away poorer students than all the others,” Finn said. “If you want to get lost in the back corner, whether you’re disruptive or not … you disconnect yourself from any instruction at all.”
But if class-size reduction works because students change their behavior, wouldn’t it work better if teachers and principals changed what they’re doing, too? That’s the question Elizabeth Graue at the University of Wisconsin-Madison has been studying at schools involved in a project called SAGE (Student Achievement Guarantee in Education).
Smaller classes worked best when teachers received training in how to better tailor instruction to each student’s needs and when they spent more time getting to know their students’ families.
Still, there were wide variations in the effect that smaller classes had from building to building.
“I don’t think any state program can be identified as a slam dunk,” Graue said.