Fastbridge · 551 students
7× more likely to reach low or no risk
Under 40 sessions
80+ sessions
5 completed studies · 1 Tier II + 4 Tier III
Research-based from day one
Independent studies consistently show stronger early-reading growth when students receive sustained, one-to-one Once tutoring. Explore the headline findings, methods, and full reports.
ESSA Tier II · LXD Research
0.46standard deviations
Effect for below-median kindergarteners completing 80+ sessions.
Measured on Fastbridge in a 2024–25 quasi-experimental study. The result was statistically significant at p < 0.001.
5
completed ESSA-aligned studies
1
ESSA Tier II study
4
ESSA Tier III studies
Next level of evidence
Tier I randomized trial in progress
2025 study highlights
Findings from the 2024–25 school year
Across two assessment systems, the strongest outcomes appeared when students received roughly 20 hours of Once instruction—80 focused, 15-minute sessions across the year.
7×
i-Ready · 822 students
More than 20 percentile points of growth
Among the 542 students who began below the national median, those receiving 20 hours of one-to-one tutoring gained more than 20 percentile points on average.
Flagship evidence
0.46 SD
Quasi-Experimental Study on Impact of Once on Kindergarten Reading Growth 24-25 as Measured by Fastbridge
The first ESSA Tier II quasi-experimental study on Once — LXD Research finds a 0.46 standard deviation effect (p<0.001) for kindergarten students who received 80+ Once tutoring sessions.
All studies & reports
Every efficacy study, research brief, conference presentation, and implementation report currently published by Once.
2025Highlighted year
Quasi-Experimental Study on Impact of Once on Kindergarten Reading Growth 24-25 as Measured by Fastbridge
The first ESSA Tier II quasi-experimental study on Once — LXD Research finds a 0.46 standard deviation effect (p<0.001) for kindergarten students who received 80+ Once tutoring sessions.
End-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.
End-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.
Reflections 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.
2024
New 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.
End-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.
End-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.
Effects 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.
2023
New 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.
End-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.
We'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.
Mid-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.
Partner 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.