"The Orton-Gillingham Approach has been in use since the 1930s. An intensive, sequential phonics-based system teaches the basics of word formation before whole meanings. The method accommodates and utilizes the three learning modalities, or pathways, through which people learn—visual, auditory and kinesthetic. Unlike some scripted and rigid reading programs, the Orton-Gillingham Approach is a system that allows for flexibility." Wiki
The Florida Center for Reading Research reported in 2006 that it was unable to identify any empirical studies examining the efficacy of the approach specifically as described in Orton-Gillingham training materials. Thus there was no direct research evidence to determine its effectiveness, although there are a variety of studies of derivative methods that incorporate aspects of Orton-Gillingham in combination with other techniques.
An overview of all reported studies of Orton-Gillingham derivative methods, such as Alphabetic Phonics or Project Read, revealed only a dozen studies with inconsistent results and a variety of methodological flaws. Despite these conclusions, the article does provide a detailed overview of the available research, which viewed most favorably would show some evidence of benefit from classroom use of OG methods with first graders, and use in special education or resource room settings with older children with learning disabilities.
In July 2010, a US Department of Education agency reported that it could not find any studies meeting its evidence standards to support the efficacy of Orton-Gillingham based strategies.
One study found it was effective for students who were English Language Learners.
Research has indicated the system is effective in remediating instruction for students with dyslexia. Although further research mentions that its efficacy is yet to be determined.