6 completed studies · 1 Tier II + 5 Tier III
Latest study · Tangipahoa Parish
6
completed ESSA-aligned studies
1
ESSA Tier II study
5
ESSA Tier III studies
Next level of evidence
Tier I randomized trial in progress
Flagship evidence · 2025
0.46 SD
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.
Latest findings · 2026
24→68%
of Tangipahoa kindergartners reading at or above benchmark
DIBELS · 1,263 students · 14 schools
43rd→61st
median national percentile
58%
of students starting below benchmark reached it by spring
39%
lowest-hours group
86%
highest-hours group
The share reaching benchmark rose as instructional hours increased.
2025 study highlights
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.
2025 study · Fastbridge · 551 students
Under 40 sessions
80+ sessions
2025 study · i-Ready · 822 students
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.
Every efficacy study, research brief, conference presentation, and implementation report currently published by Once.
A district-wide LXD Research study of 1,263 Tangipahoa kindergartners found DIBELS benchmark attainment rose from 24% to 68%. The results are correlational.
Once is partnering with Johns Hopkins University on a multi-year randomized controlled trial to rigorously measure program impact on early-literacy outcomes.
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.
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.
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.
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.
Once is featured in an NSSA report studying the potential benefits of paraprofessionals as tutors in early elementary classrooms.
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.
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.
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.
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.
Once Research Report for Kindergarten 22-23 from LXD Research, measuring Once's impact on kindergarten reading achievement during the 2022-23 school year.
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.
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.
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