|Photo: Arthur VanderVeen|
In Bloom’s study, students who learned a topic through tutoring, combined with regular formative assessment and corrective instruction, performed two standard deviations (2 sigma) better than students who received conventional classroom instruction. In other words, the average tutored student performed better than 98 percent of the students in the traditional classroom.
What was the difference? Personalization. Personalization is defined as differentiating instruction and providing regular corrective feedback based on the needs of each student. This included personalizing both path and pace--identifying and addressing missing prerequisite knowledge, and spending more time where necessary to ensure students achieved mastery of topics before moving on.
In a more recent study, Roland Fryer at Harvard’s EdLabs evaluated the impact on student achievement of five instructional practices implemented in Houston ISD’s Apollo 20 program, including high-dosage tutoring. Secondary students who received math tutoring outperformed their peers in the treatment schools who did not receive tutoring by 0.4 sigma, or 200 percent (32).
Of course, the “problem” in the 2 Sigma Problem is that individual or small-group tutoring is “too costly for most societies to bear on a large scale.” (The Apollo 20 program is reported to cost $29 million annually for nine schools.) The challenge, then, as Bloom framed it, is this:
Can researchers and teachers devise teaching-learning conditions that will enable the majority of students under group instruction to attain levels of achievement that (at present) can be reached only under good tutoring conditions?