Twin studies have shown that genetic factors can account for as much as 82 percent of the variability in children's reading skills. But while genes might set the bar for reading potential, a new study published April 23 in Science shows that teachers play a leading role in helping kids reach it.

"When children receive more effective instruction, they will tend to develop at their optimal trajectory," said study lead author Jeanette Taylor in a prepared statement. "When instruction is less effective, then children's learning potential is not optimized and genetic differences are left unrealized."

Taylor and colleagues from Florida State University in Tallahassee studied 280 identical and 526 fraternal twin pairs in the first and second grades in a diverse sample of Florida schools. Using the Oral Reading Fluency test as a measure of reading skill, the researchers determined how much of the variability in reading achievement was due to genetic factors. The twins' classmates' Oral Reading Fluency test scores were used to measure teacher quality—if test scores improved across the class, the gain was attributed to a high-quality teacher.

The researchers found that good instruction promoted stronger reading development. Without it, children were less likely to reach the potential conferred by their genes. "When teacher quality is very low, genetic variance is constricted, whereas, when teacher quality is very high, genetic variance blooms," they report. While teacher quality appears to be an important contributor, other classroom factors, such as classmates and resources, might also influence reading ability, the researchers noted.

With teacher quality gaining increasing attention in U.S. political circles, the study highlights the potential for education to moderate the genetic effects on early reading. "Putting high-quality teachers in the classroom will not eliminate variability among students nor guarantee equally high achievement from all children, but ignoring teachers as a salient contributor to the classroom environment represents a missed opportunity to promote children's potential in school and their success in life," the researchers concluded.

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