Several studies have evaluated the effectiveness of FOCAL SKILLS through controlled comparisons with other methods.
The FOCAL SKILLS Advantage is a concise summary and analysis of the research findings.
The FOCAL SKILLS Approach: An Assessment explains the basic assumptions and principles of FOCAL SKILLS and presents research supporting the claim that FOCAL SKILLS accelerates the acquisition of proficiency in a second language. Here is an excerpt from Thomas Leverett's review (TESL-EJ, Vol. 2, No. 3, January 1997) of the book in which this chapter appears:
I had looked forward to this volume because of my familiarity with the Focal Skills System, in which the language curriculum is redesigned so that beginning students are immersed almost entirely in a listening module (with electives) until they have mastered listening; they then move on to a reading module, followed by a writing module. I cannot do justice to the system here, but a chapter by Ashley Hastings, "The FOCAL SKILLS Approach: An Assessment," does. Written by the founder of the approach, the article presents the system itself, and evidence that it works. As the system is based directly on elements of Krashen's theories (e.g., a focus on receptive skills first; grammar and pronunciation not taught overtly), it is surprising that it hasn't received more attention to date, considering the popularity Krashen's theories have enjoyed in the last decade. Furthermore, Focal Skills programs have been functioning successfully in widely diverse locations (Japan, Virginia, Mississippi, Washington State, and UW-Milwaukee, to name a few) for quite some time. Just as communes that were based on B.F. Skinner's philosophy long outlasted the popularity of the philosophy itself, this system may well outlast the popularity of Krashen's theories, which are under attack from all sides. In any case, it remains as a testament to Krashen's influence."
A Comparison of English Proficiency Gains in One Focal Skills and Two Traditional ESL Programs, a 1998 Shenandoah University master's thesis by Bai Yu, found that FOCALS SKILLS was more effective in improving students' language proficiency both overall and in specific skills.