If the random assignment experiment is the gold standard of education research, the twin study is surely in the running for silver status. Studies of twins allow researchers to compare subjects with identical genetics but who experience differences in their environments.

With so many of the variables associated with student achievement related to factors outside the school, a team of researchers from Florida State University used data from sets of twins to look at the impact that teacher quality has on students' reading development. The finding--perhaps not a bombshell, but in a nutshell: the quality of the teacher has a direct influence on young children's reading outcomes.

Levels of teacher quality were determined using value-added data from full classes of first and second grade students on tests of oral reading fluency, which is closely associated with the development of comprehension skills. Twins (including identical twins who share 100 percent of their genes) who had high quality teachers had higher fluency scores than their siblings with lower quality teachers.

The study concludes that "reading will not develop optimally in the absence of effective instruction." While not a novel idea, it reinforces the critical need for not only evaluation strategies that identify whether teachers are effective, but also teacher preparation in scientifically based reading instruction, both of which are sorely lacking throughout the country. Florida, through its "Just Read, Florida!" initiative is ahead of most states in embracing the science of reading, and has seen a big rise in student achievement in reading over the last decade. Yet the study shows much work remains.

The researchers diplomatically state that "when instruction is less effective, then children's learning potential is not optimized." A more blunt translation: as early as first grade, children's life trajectories are negatively impacted by poor reading instruction.