Small groups of 3-5 are as effective as 1-to-1 instruction

Although not conclusive for making individual student-level decisions, there is compelling research indicating that instruction provided to groups of 3 to 5 students is as effective as 1-to-1 instruction, even for the most at-risk students (Elbaum, Vaughn, Hughes, & Moody, 2000).

Harn, B.A., Linan-Thompson, S., Roberts, G. (2008). Intensifying Instruction: Does Additional Instructional Time Make a Difference for the Most At-Risk First Graders? Journal of Learning Disabilities, 41 (2) p.115-125.