Research
Research-based from day one
Once is built on the Science of Reading and measured rigorously. Read our efficacy studies, conference presentations, and implementation research.
0.46 SD
effect size (p<0.001)
Flagship result
Kindergarteners receiving Once gained 0.46 standard deviations on Fastbridge — substantially larger than other high-quality tutoring programs
LXD Research's 2024-25 quasi-experimental study (ESSA Tier II) measured kindergarten students who started below the 50th percentile nationally and completed 80+ Once tutoring sessions. The finding is statistically significant at p<0.001.
Read the full studyAll studies & reports
2025-26 JHU–Once Randomized Controlled Trial Randomization Brief
Once is partnering with Johns Hopkins University on a multi-year randomized controlled trial to rigorously measure program impact on early-literacy outcomes.
ReadEnd-of-Year Report: Impact of Once on Kindergarten Reading Growth 24-25 as Measured by Fastbridge
An LXD Research study of 551 kindergarteners across 35 Southeast schools shows students who completed 80+ Once sessions were 7× more likely to reach low/no risk by spring.
ReadEnd-of-Year Report: Impact of Once on Kindergarten Reading Growth 24-25 as Measured by i-Ready
A new LXD Research study of 822 kindergarten students found those receiving 20+ hours of 1:1 Once tutoring grew over 20 percentile points on i-Ready.
ReadReflections on the 2025 National Student Support Accelerator Annual Research Conference
Our second year at the NSSA Annual Research Conference — a serious group sharing serious ideas on effective high-impact tutoring, with broader district and state representation.
ReadNew National Student Support Accelerator Report Studies Employing Paraprofessionals as High-Impact Tutors
Once is featured in an NSSA report studying the potential benefits of paraprofessionals as tutors in early elementary classrooms.
ReadEnd-of-Year Report: Impact of Once on K Reading Growth 23-24 as Measured by i-Ready
LXD Research's 2023-24 end-of-year analysis across three schools showed kindergarten students on Once grew from the 38th to the 67th percentile nationally on i-Ready.
ReadEnd-of-Year Report: Impact of Once on K Reading Growth 23-24 as Measured by aimswebPlus
A gap-closing impact study — kindergarten students using Once at an Ohio school grew faster than their national peers and the rest of the district on aimswebPlus.
ReadEffects of High-Impact Tutoring on Early Literacy Outcomes: A Pilot Study of a 1:1 Program With Existing Staff
A 2022-23 Stanford NSSA pilot study of Once tutoring in a large urban district — students receiving Once scored two points higher on end-of-year DIBELS than peers.
ReadNew Report Shares Promising Practices for Implementing High-Dosage Tutoring in American Schools
Accelerate and Mathematica release a new report summarizing best practices and lessons learned from their first cohort of Call to Effective Action grantees, including Once.
ReadEnd-of-Year Report: Impact of Once on K Reading Growth 22-23
Once Research Report for Kindergarten 22-23 from LXD Research, measuring Once's impact on kindergarten reading achievement during the 2022-23 school year.
ReadWe've Been Awarded a Call to Effective Action Grant from Accelerate
Once is a second-time grantee for Accelerate's Call to Effective Action, enabling us to conduct research trials demonstrating efficacy before scaling our impact.
ReadMid-Year Report: Impact of Once on K Reading Growth 22-23
Preliminary Research Report for Once Kindergarten Tutoring Fall 2022 from LXD Research, showing impact on kindergarten reading achievement in the first half of the school year.
ReadNational non-profit Accelerate selects Once to explore sustainable models for high-impact tutoring
Once is honored to be selected as a grantee for Accelerate's Call to Effective Action — a national effort to develop and scale sustainable, cost-effective high-impact tutoring.
ReadPartner with us
Every school is a research partner
Once gives every school and district top-tier efficacy data on their implementation at no additional cost. Let's study your students together.