One-on-One Learning is the Sigma
By Luke Rickford
Every summer, in late June, I meet a new group of international students from a high school in China. They brave the long flight to California to visit colleges, practice their English, and see the sights—but mostly, they come for the intensive SAT prep course that I teach. For the next three weeks, I will spend four hours a day reviewing test-taking strategies and grammar rules in a hotel conference room big enough to accommodate two dozen tired-but-determined teenagers. But after just one day, I can already predict who will improve the most. That’s about how long it usually takes for certain students to begin approaching me for extra support.
Chart based on The 2 Sigma Problem; Bloom; JSTOR 2006
In 1984, Benjamin Bloom’s landmark 2-sigma study highlighted the powerful impact of individual instruction on student learning outcomes. The study compared students who learned in three different environments: conventional classrooms, "mastery learning" classrooms with adaptive curriculum, and sessions with a good tutor for each student (or two or three). The mastery learning group outperformed 84% of conventional students, a significant difference of one standard deviation, or 1 sigma. But the best outcomes by far came from the students who received tutoring. These students outperformed 98% of conventional classroom learners—they weren’t just learning better; they were learning 2 sigma better. In pedagogy, the scientific study of educational methods, researchers get excited when a new approach outperforms the old way by 15%. Bloom’s study showed that in the ocean of education, if conventional classroom instruction was a goldfish, tutoring was a blue whale.
In twenty years of teaching, from Boston to Los Angeles and back to my beloved Bay Area, I’ve seen a lot of different classrooms. Some are better than others, due to the availability of vital resources, an abundance of high-quality educators, or the culture of achievement and support that an engaged local community can bring. But wherever I travel and whatever student population I work with, one constant stands out: the students who seek out (and receive!) individual support learn faster, retain more of what they learn, and are more likely to demonstrate true mastery and independence.
Don’t get me wrong—I love classroom teaching! Whether students are actively learning from each other through productive discussion, or even passively gaining new insight from listening to a classmate work through a problem on the whiteboard, a well-maintained classroom offers countless opportunities for meaningful, dynamic education. Meanwhile, tutoring gives students and educators the chance to connect in a more flexible environment where “what does this individual need most, right now?” is not one of many questions informing the study plan; it’s the only question. This simple shift in focus creates the powerful 2-sigma effect that Bloom first noticed over forty years ago, and which continues to inform our approaches as research-based educators today.
In tandem, thoughtful classroom instruction supported by tutoring creates a rising tide of mastery. Students benefit from the accumulated momentum of multiple levels of learning: they hop on their boards and catch the wave at school, then get a second boost through tutoring and small group instruction, until they can stand up on their own and ride for as long as they want.
Luke leads Grupology’s private instruction for high school students. His favorite pastimes include teaching Murakami’s “Super Frog Saves Tokyo,” catering to the whims of a two-year-old pug, and chasing frisbees (though usually not all at the same time).
Citations:
BLOOM, B. S. (1984). The 2 Sigma Problem: The Search for Methods of Group Instruction as Effective as One-to-One Tutoring. Educational Researcher, 13(6), 4-16. https://doi.org/10.3102/0013189X013006004 (Original work published 1984)
