Impact of Preschool on School Preparedness: Evidence from a Nationwide RCT in Finland

Last registered on October 15, 2021

Pre-Trial

Trial Information

General Information

Title
Impact of Preschool on School Preparedness: Evidence from a Nationwide RCT in Finland
RCT ID
AEARCTR-0008061
Initial registration date
October 15, 2021
Last updated
October 15, 2021, 6:13 PM EDT

Locations

Region

Primary Investigator

Affiliation
VATT Institute for Economic Research

Other Primary Investigator(s)

PI Affiliation
Aalto University School of Business
PI Affiliation
Aalto University

Additional Trial Information

Status
On going
Start date
2021-08-11
End date
2025-12-31
Secondary IDs
Prior work
This trial does not extend or rely on any prior RCTs.
Abstract
We designed, together with Finland's Ministry of Education and Culture, a randomized experiment to test the effect of preschool curriculum on the school preparedness of five year old children born in 2016-2017. Our intervention advances the starting age of mandatory preschool by one year from age 6 to age 5. In Finland, compulsory schooling starts at age 6 in preschools which are often attached to day care centers. At age 7 elementary school begins. A special bill was passed by the parliament to mandate preschool for the 5 year old children in the treatment group. The treatment group attends preschool for two years instead of one. In the absence of treatment, most of the treatment group would attend day care and some would stay home at age 5. The treatment group follows a curriculum made by educational specialists specifically for the two-year preschool.

Our main outcomes are arithmetic and reading skills, psychosocial skills and self esteem. They are measured during the first grade of elementary school, two years after the intervention started.
External Link(s)

Registration Citation

Citation
Harjunen, Oskari, Ramin Izadi and Matti Sarvimäki. 2021. "Impact of Preschool on School Preparedness: Evidence from a Nationwide RCT in Finland." AEA RCT Registry. October 15. https://doi.org/10.1257/rct.8061-1.0
Experimental Details

Interventions

Intervention(s)
Intervention:
The two year preschool intervention advances the starting age of mandatory preschool by one year from age 6 to age 5. In Finland, compulsory schooling starts at age 6 in preschools which are often attached to day care centers. At age 7 elementary school begins. A special bill was passed by the parliament to mandate preschool for the 5 year old children in the treatment group. The treatment group attends preschool for two years instead of one. The treatment group follows a curriculum made by educational specialists specifically for the two-year preschool. The curriculum is centrally directed by the Ministry of Education but locally adapted my municipal boards of education. There are potentially large variations across municipalities in the exact content of the curriculum. In general, relative to day care, preschool curricula are more structured including sessions with directed learning of school skills.

Counterfactual:
In the absence of treatment, at age 5, most of the treatment group would attend day care and some would stay home.
Intervention Start Date
2021-08-11
Intervention End Date
2024-06-30

Primary Outcomes

Primary Outcomes (end points)
- Arithmetic and reading skills.
- Psycho-social skills and self esteem.
Primary Outcomes (explanation)
We will examine the impact of the intervention on school preparedness as measured by standardized tests on arithmetic and reading skills, psycho-social skills and self-esteem. The first follow-up will be conducted roughly 14 months (during the second year of preschool) and the second follow-up 26 months (during first grade of elementary school) after the start of the intervention. The survey instrument for the first follow-up will be finalized during the summer of 2022 and for the second follow-up during the summer of 2023. Each four primary outcomes are composed of multiple questionnaire items. We will update our trial registration with details of the measures once the survey instruments are finalized.

Secondary Outcomes

Secondary Outcomes (end points)
Individual test items or sub components of the primary outcomes composites.
Secondary Outcomes (explanation)
We will update our trial registration with details of the measures once the survey instruments are finalized.

Experimental Design

Experimental Design
The experimental program targets all eligible day care centers in Finland. Eligibility was determined by the ability to offer both services: day care and preschool. The number of eligible day care centers in each municipality was estimated by a survey. Based on the survey, municipalities with fewer than 5 eligible daycare centers formed their own experimental sample (small RCT). Based on this sample split, we run two separate designs in parallel.

Small RCT (randomization at the municipal level)
- 83 municipalities with estimated more than one but less than five eligible day care centers.
- Randomization is done at the level of the municipality.
- 41 municipalities are randomized into treatment group.
- In the treated municipalities all eligible day care centers start offering two-year preschool.

Large RCT (randomization at the day care center level)
- 63 out of 92 large municipalities are first randomized to participate in the experiment using stratified sampling.
- The strata were defined by geographical areas and the number of eligible daycare centers.
- All children born in 2016-2017 are assigned to a day care center based on current customership, or distance.
- Within each of the 63 municipalities in the sample, 40% of eligible day care centers were randomly assigned to the treatment group
- Students that are assigned to a treatment center are offered two-year preschool.
Experimental Design Details
Not available
Randomization Method
For both designs (small and large municipalities), re-randomization was applied to guarantee covariate balance. We simulated one million potential assignment vectors and chose from them 2000 with the best covariate balance according to the Mahalanobis distance criterion. The final treatment assignment vector was drawn from among those 2000 potential assignment vectors. The covariates used for the criterion were:

Small RCT (municipal level covariate averages/shares)
- Geographical/administrative area
- Foreign born
- Earnings
- Secondary education
- College education

Large RCT (day care center level covariate averages/shares)
- Herfindahl index for language concentration
- Earnings
- Single parents
- Primary education
- Secondary education

In addition, in order to stay within the budget, we balanced on the number of children and cost per child to minimize variation in the expected cost of the experiment.

The re-randomization algorithm was implemented using an R script with a random number seed. The seed was generated by requesting the current computer clock time by email from our Ministry of Education partners.
Randomization Unit
Small RCT: Randomization is done at the level of the municipality.
Large RCT: Randomization is done at the level of the day care center.
Was the treatment clustered?
Yes

Experiment Characteristics

Sample size: planned number of clusters
Small RCT: 83 clusters (municipalities).
Large RCT: 752 clusters (day care centers).
Sample size: planned number of observations
For the cohort born in 2016 Small RCT: 3700 children. Large RCT: 14700 children. The cohort born in 2017 is expected to have 0.95 times as many children. In total, the above figures are multiplied by 1.95 to arrive at an estimated number of observations. Total children in across two cohorts: Small RCT: 7200 children. Large RCT: 28600 children.
Sample size (or number of clusters) by treatment arms
Small RCT: 41 small municipalities in treatment, 42 small municipalities control.
Large RCT: 299 day care centers in treatment, 453 day care centers in control.
Minimum detectable effect size for main outcomes (accounting for sample design and clustering)
Large RCT: We are powered to detect a minimum of 0.1 standard deviation treatment effect for a continuous test variable, for example, mathematics. To determine the MDE, we assumed 80% power, test size of 0.05, and intra-cluster correlation of 0.2. Small RCT: We are powered to detect a minimum of 0.25 standard deviation treatment effect for a continuous test variable, for example, mathematics. To determine the MDE, we assumed 80% power, test size of 0.05, and intra-cluster correlation of 0.2. We expect to improve precision by including baseline measures as controls.
IRB

Institutional Review Boards (IRBs)

IRB Name
Research Ethics Committee, Aalto University
IRB Approval Date
2021-06-16
IRB Approval Number
D/552/03.04/2021