2.7 months
additional reading growth
beyond typical kindergarten progress, according to the study’s translation of the effect size
Once impact · ESSA Tier II evidence
An estimated 2.7 additional months of reading growth
That’s LXD Research’s study-specific estimate for kindergarten students below the national median who completed 80+ Once sessions, compared with similar students receiving their schools’ typical reading support.
LXD Research’s estimate
2.7months
Approximate additional reading growth beyond typical kindergarten progress.
The report translates this study’s 0.46 standard-deviation effect into a more familiar outcome. Measured on FastBridge; p < 0.001.
The study at a glance
What the result means for students
Researchers estimated that students completing 80+ Once sessions gained about 2.7 more months of reading growth than similar students receiving typical school support.
0.46 SD
effect versus matched peers
a statistically significant difference on FastBridge (p < 0.001)
80+
sessions completed
the participation level associated with the study’s strongest result
How the study worked
A fairer comparison than a simple before-and-after
LXD Research conducted the study in a large southeastern school district using data from the 2024–25 school year.
Step 1
Start with similar students
Researchers focused on kindergarten students who began the year below the 50th percentile nationally on FastBridge.
Step 2
Match treatment and comparison groups
Students were matched using beginning-of-year proficiency and demographic characteristics rather than assigned at random.
Step 3
Compare reading growth
The study estimated the difference in FastBridge growth for students who received 80 or more Once tutoring sessions.
What this means for schools
The strongest result came with consistent participation
Once is designed around a simple operating model: one adult, one student, one scripted 15-minute lesson each school day.
Students completing 80+ sessions averaged more than two sessions per week. For district leaders, the finding makes consistent delivery—not just program selection—a central part of the impact story.
See Once for schoolsRead the evidence
Go deeper into the study
Review the research summary for context, or download LXD Research’s full report for the study design, model, results, and technical detail.
Bring consistent one-to-one reading support to your district
Could Once fit your early-literacy goals?
Talk with our team about staffing, implementation, and how Once could fit your early-literacy goals.