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The LEAP study
Last registered on September 08, 2020


Trial Information
General Information
The LEAP study
Initial registration date
September 07, 2020
Last updated
September 08, 2020 9:35 AM EDT
Primary Investigator
Aarhus University
Other Primary Investigator(s)
Additional Trial Information
Start date
End date
Secondary IDs
This trial is based on a population-representative sample of 3–6-year-old Danish children from 154 preschools centers. The centers participated in a cluster-randomized evaluation of three variations of a language-literacy focused curriculum, LEAP (Language Education Activities for Preschoolers) comprising 40 twice-weekly 30-min lessons. Prior to the intervention, educators from the treatment institutions were trained for two days. The intervention aimed at investigating the effects associated with two components commonly seen in systematic explicit language and literacy interventions - group size and scripted lessons with aligned activities – on child outcomes when implemented at scale in a Danish preschool setting.
External Link(s)
Registration Citation
Bleses, Dorthe. 2020. "The LEAP study." AEA RCT Registry. September 08. https://doi.org/10.1257/rct.6412-1.0.
Sponsors & Partners
Experimental Details
The sample consists of four groups: LEAP-OPEN, LEAP-LARGE, LEAP-SMALL, and business as usual (BAU).
In LEAP-OPEN, educators followed the scope and sequence of the intervention, but were allowed to determine the instructional activities for each of 40 lessons (i.e., they received no scripted lessons). In LEAP-LARGE and LEAP-SMALL conditions involved educators’ implementation of a scope and sequence of objectives using scripted lessons provided to whole-class and small groups, respectively.
The lesson plans were crafted so that each lesson emphasizes one objective for each of two learning domains (e.g., phonological awareness and print knowledge). Educators were provided a set of materials required to implement these lessons, including a suitcase, picture cards, and a “booklet” for each child with some printed material, but most lessons utilized toys or other material prevalent in all preschools. Each lesson plan included two components: (1) the LEAP lesson plan itself, which soft-scripted a sequence of step-by-step instructions for the aligned language and literacy activity as well as suggested language that educators could use to support children’s learning during each activity, and (2) a ‘Learners’ Ladder,’ which presented specific scaffolding strategies that educators could use for children who found a given lesson too easy or too difficult.
The activities included memory games, nursery rhymes, children’s songs, storytelling using pictures, and various activities that involved moving around in the preschools. Each type of activity was repeated four to five times across the 40 lessons to support the four learning domains. All types of activities were piloted in 16 preschools and educators provided oral and written feedback to help refine activities prior to implementation.
Intervention Start Date
Intervention End Date
Primary Outcomes
Primary Outcomes (end points)
The (Danish) Language Assessment of Children: 3–6 instrument (Bleses et al., (2010), “The internal validity and acceptability of the Danish SI-3: A language screening instrument for 3-year-olds”, Journal of Speech, Language, and Hearing Research (53), p. 490-507) , which is a part of a national screening program, including all municipalities participating in the present study.
Primary Outcomes (explanation)
Secondary Outcomes
Secondary Outcomes (end points)
Secondary Outcomes (explanation)
Experimental Design
Experimental Design
The study randomized preschool institutions (within municipalities) in four groups of approximately equal size. Three groups were treatment groups, and the fourth served as a control group.
The sample was randomized into four groups (stratified at municipal level): LEAP-OPEN, LEAP-LARGE, LEAP-SMALL, and business as usual (BAU), which served as a control.
Prior to the intervention, educators from the treatment institutions were trained for two days where they also received instructions on how to identify the various learning objectives and discussed how the specific content could be implemented. Preschool teachers in control institutions participated in a one-day workshop on topics relevant to the daily routines in a preschool.
In LEAP-OPEN and LEAP-SMALL, classrooms of around 16 children were organized in groups of up to six children Two educators in each classroom were randomly assigned to two groups of children within a classroom, and provided the LEAP intervention to these intact groups for the duration of the 20-week period. In LEAP-LARGE, all children in the classroom participated in the same group, and each lesson was implemented by two educators in a classroom.
Experimental Design Details
Randomization Method
Randomization done by a computer
Randomization Unit
Preschools (stratified by municipalities)
Was the treatment clustered?
Experiment Characteristics
Sample size: planned number of clusters
154 preschools
Sample size: planned number of observations
6,706 children
Sample size (or number of clusters) by treatment arms
The number of children (number of preschools) in the LEAP-OPEN, LEAP-SMALL, LEAP-LARGE, and BAU groups are: 1,701 (38), 1,726 (40), 1,568 (36), BAU (40). The intervention included all preschools from eight municipalities located in different parts of Denmark: Aabenraa, Faxe, Gentofte, Halsnaes, Copenhagen, Lejre, Rudersdal, and Skive.
Minimum detectable effect size for main outcomes (accounting for sample design and clustering)
IRB Name
IRB Approval Date
IRB Approval Number
Post Trial Information
Study Withdrawal
Is the intervention completed?
Is data collection complete?
Data Publication
Data Publication
Is public data available?
Program Files
Program Files
Reports, Papers & Other Materials
Relevant Paper(s)