Genetics play the biggest role in determining how fast a child learns to read, but a good teacher can make a measurable difference as well, according to a study released Thursday.
Florida State University used twins assigned to different classrooms to develop the conclusions.
Researchers studied more than 550 first- and second-grade classrooms with at least one identical twin and more than 1,000 classes with at least one fraternal twin.
Among the identical twins, 42 pairs out of 280 pairs showed significant differences in reading improvement during the year studied, said lead researcher Jeanette Taylor, an associate professor of psychology at Florida State.
In each case, the teachers also had significantly different quality scores. Twins with similarly good teachers got similar scores.
"If you have identical twins, they should do very similarly in school," Taylor said.
Teachers whose students showed the greatest average one-year improvement in the number of words they could read out loud in one minute were considered the best teachers for the purpose of the study.
The study published in the journal Science was paid for by the National Institute of Child Health and Human Development, which is part of the National Institutes of Health.
The study tapped information from a national effort to gather detailed student data in every state, which may enable others to confirm or disprove other long-held assumptions about education.
Previous reading research on unrelated children could not pinpoint how much differences in achievement were associated with genes, home life or the classroom, according to Taylor.
Reaching their potential
The study shows teacher quality is one reason for the differences between the achievements of twins, but it cannot explain the whole difference, Taylor said. Since these pairs were all in two different classrooms, other possible factors include how well behaved classmates are.
The researchers believe their results showed the best teachers made the biggest difference in learning achievement. Genetic differences between students seemed to disappear in classrooms taught by less effective teachers, because children don't reach their potential, the researchers found.
The director of the University of Illinois-Chicago Center for Literacy found the methodology of the study fresh and interesting but was concerned people would think the research revealed more about teachers than it does.
"The word teacher or teacher quality is being used here as a shorthand for the kids' entire experience in the classroom," said Tim Shanahan, professor of urban education at the University of Illinois.
The scores could have been influenced by the other students in the room, what administrative support the teacher was getting or what materials and curriculum she has, as well as the teacher's education, training and skill at keeping kids on task.
"Good classrooms are all alike; they maximize kids' potential. Poor classrooms are not only poor in one way; they are poor in multiple ways," Shanahan said.
Shanahan argues that all these factors are variable and can change for any teacher, given enough resources and training.