An LXD Research study of 257 kindergartners in a high-poverty South Carolina district found the median student rose from the 21st to the 39th national percentile on MAP Growth Reading. The results are correlational.
Study at a glance
257
students
9
schools
63
median sessions
Growth relative to national norms
Students growing at the same rate as the national norm group would hold the same percentile all year. These students climbed 18 points.
+18
percentile points
MAP benchmark
Fall
17%
Spring
47%
The share scoring well below benchmark fell from 47% to 25%. Of students who started well below, 28% reached benchmark by spring.
Sessions delivered
+8
1–19
n=17
+10
20–39
n=32
+11
40–59
n=66
+17
60–79
n=102
+20
80+
n=40
All 257 students, fall to spring. Prior Once research links 80 or more sessions with the strongest gains.
Source: LXD Research, 2025–26 South Carolina kindergarten descriptive outcomes study. Results are descriptive and correlational because the study did not include a comparison group.
A high-poverty school district in South Carolina used Once with 257 kindergartners across nine elementary schools during the 2025-26 school year. A new LXD Research study tracked those students on NWEA MAP Growth Reading in the fall, midyear, and spring. The study is descriptive and correlational: it had no comparison group, so it cannot show that Once caused the gains.
Before the district adopted Once, districtwide reading proficiency stood at about 46%, compared with 60% statewide. The district chose Once to intervene early, in line with South Carolina’s Read to Succeed Act.
MAP percentiles compare each student with a national norm group. A student who grows at the same rate as that group keeps the same percentile all year. Holding steady means a typical year of growth. Moving up means faster growth than the national norm.
The median kindergartner in this study moved from the 21st percentile in the fall to the 32nd percentile at midyear and the 39th percentile in the spring. That is an 18-point gain relative to national norms over one school year.
The whole distribution moved up, not just the middle. The box in the chart above shows the middle half of students. In the fall, that group fell roughly between the 9th and 35th percentiles. By spring, it spanned roughly the 21st to the 68th.
The share of kindergartners scoring at or above the MAP benchmark rose from 17% in the fall to 47% in the spring. The share scoring well below benchmark fell from 47% to 25%.
Among students who started the year below or well below benchmark, 37% reached benchmark by spring. Among those who started well below, 28% did.
Tutoring support often drifts toward students who attend most consistently or who are already close to proficiency. This district avoided that. Students in the lowest fall achievement quintile received a median of 69 sessions and 12.0 hours of instruction. Students in the average quintile received 41 sessions and 6.2 hours, and those in the highest quintile received 43 sessions and 5.8 hours.
Students who received more Once sessions showed larger percentile gains from fall to spring. Across all students, the median gain rose from +8 points for 1 to 19 sessions to +20 points for 80 or more sessions. Students who began below the 50th percentile showed a similar pattern, rising from +11 to +20 points.
This matches earlier Once research, which links 80 or more sessions with the strongest gains for students reading below grade level.
The median student received 63 sessions, or 10.1 hours of instruction. The district delivered a median of 71% of scheduled sessions, which compares favorably with national tutoring implementations, where 25% to 50% of planned dosage is common. Even so, only 16% of kindergartners reached the 80-session threshold.
The researchers recommend that districts make 80 sessions an operational goal and track delivery against a target of 80% of scheduled sessions.
These results are encouraging, especially for a first-year implementation in a high-poverty district. They should still be read with the study’s limitations in mind: there was no comparison group, the researchers could not identify how dosage levels were set for each student, and the study did not include formal measures of implementation fidelity.
Read the full LXD Research study and contact Once if you want to talk about what early reading tutoring could look like in your schools.