5 Results

Of 5,088 unique citations, we excluded 3,961 citations during title and abstract screening. Of the 552 remaining citations we could locate for full-text eligibility assessment, we excluded 375 citations. We included the remaining 133 studies (reported in 159 manuscripts) in our scoping review (see Figure 1).

5.1 Characteristics of Sources of Evidence

We provide a summary of characteristics of sources of evidence in Table 1. Included studies were published from 1980 to 2025 (median of 2018). Of the 133 studies, most (n = 102; 77%) are published in grey literature: 75 (56%) as a student dissertation or thesis, 19 (14%) as a student dissertation or thesis, and 8 (6%) as a preprint. Only 31 studies (23%) had a peer-reviewed journal article as the final version of record. Of the 75 student dissertation or thesis article types, 62 (83% of student manuscripts) were a doctoral dissertation, 11 (15%) were a masters thesis, and 2 (3%) were an undergraduate thesis. Most students completed dissertations and theses in partial fulfillment of degrees in education (n = 67; 89%), followed by economics (n = 4; 5%), psychology (n = 2; 3%), music (n = 1; 1%), and sociology (n = 1; 1%).

Studies collected and analyzed data from 1975 to 2025 (median of 2012). Studies predominantly included data from rural communities in their sample (n = 97; 73%), though numerous studies also included data from urban (n = 39; 29%) and suburban communities in their samples (n = 36; 27%); 32 studies (24%) did not report information on community type. Studies included data from 35 states — most predominantly from Missouri (n = 40; 30%), Colorado (n = 29; 22%), Oklahoma (n = 18; 14%), Oregon (n = 18; 14%), New Mexico (n = 13; 10%), and South Dakota (n = 12; 9%). The number of studies providing data from elementary (n = 96; 72%), middle (n = 90; 68%), and high (n = 95; 71%) schools was fairly evenly distributed across levels, with data representing all grades (except kindergarten) included in at least half the studies. Most studies did not provide information on student race/ethnicity (n = 81; 61%) nor activities on the fifth “off day” officially offered by schools or districts (n = 79; 59%).

5.2 Types of Empirical Research Evidence

We provide a summary of types of empirical research evidence in Table 2. Of the 133 included studies, most reported evidence on 4DSW effectiveness (n = 86; 65%). Among these 86 studies, 7 different methodological and statistical approaches were used: 23 studies used difference-in-differences (27% of effectiveness studies), 16 studies (19%) used descriptive statistics only, 15 (17%) studies used a before-after study design, 15 studies (17%) used a between-group (without controls) design, 7 studies (8%) used a between-group (with controls) design, 7 studies (8%) used a matched pair design, and 3 studies (4%) used a computational model design. These 86 studies provided outcome data across 9 domains: 55 studies (64% of effectiveness studies) reported on student achievement, 26 (30%) on student attendance, 16 (19%) on teacher and staff recruitment and retention, 9 (10%) on student attainment, 9 (10%) on student health status or behaviors, 7 (8%) on school climate, 6 (7%) on disciplinary incidents during school, 4 (5%) on household impacts, and 3 (4%) on juvenile crime. Most effectiveness studies (n = 45; 34% of effectiveness studies) also reported evidence on equity of 4DSW effects according to 10 domains: 28 (62% of equitability studies) on student age, 11 (24%) on community type or rurality, 11 (24%) on student socioeconomic status, 7 (16%) on student race or ethnicity, 5 (11%) on student gender identity or sex, 5 (11%) on student special education status, 3 (7%) on student English language learner status, 3 (7%) on gifted student status, and 1 (2%) on student immigration status.

Of the 81 studies (61%) that reported one type of evidence on the implementability of the 4DSW, most (n = 50; 62% of studies with implementability data) reported evidence on acceptability. These 50 studies examined satisfaction with the 4DSW among teachers (n = 34; 68%), parents (n = 20; 40%), administrators (n = 18; 36%), students (n = 15; 30%), community members (n = 11; 22%), principals (n = 8; 16%), school staff (n = 8; 16%), superintendents (n = 8; 16%), athletics (n = 2; 4%), business owners (n = 2; 4%), counselors (n = 2; 4%), and school board members (n = 2; 4%). In addition, 41 studies (51% of studies with implementability data) reported evidence on feasibility of implementing the 4DSW, and 32 (40%) reported evidence on resource use associated with switching to a 4DSW. Lastly, only 6 studies (4% of all studies) reported evidence on 4DSW as a policy priority through an explicit empirical focus on the growth of schools, districts, or states adopting the 4DSW.