Studies of small-scale "model" early-childhood programs show
that high-quality preschool can have transformative effects on human capital
and economic outcomes. Evidence on the
Head Start program is more mixed. Inputs and practices vary widely across
Head Start centers, however, and little is known about variation in effectiveness
within Head Start.
This paper uses data from a multi-site randomized
evaluation to quantify and explain variation in effectiveness across Head Start
childcare centers. It answers two questions: (1) How much do
short-run effects vary across Head Start centers? and (2) To what extent do
inputs, practices, and child characteristics explain this variation?
To answer
the first question, the author uses a selection model with random coefficients to
quantify heterogeneity in Head Start effects, accounting for non-compliance with
experimental assignments. Estimates of the
model show that the cross-center standard deviation of cognitive effects is
0.18 test score standard deviations, which is larger than typical estimates of variation
in teacher or school effectiveness.
Next, the paper assesses the role of observed
inputs, practices and child characteristics in generating this variation,
focusing on inputs commonly cited as central to the success of model programs.
The results show that Head Start centers offering full-day service boost
cognitive skills more than other centers, while Head Start centers offering
frequent home visiting are especially effective at raising non-cognitive
skills.
Head Start is also more
effective for children with less-educated mothers. Centers that draw more
children from center-based preschool have smaller effects, suggesting that
cross-center differences in effects may be partially due to differences in
counterfactual preschool options.
Other key inputs, including the
High/Scope curriculum, teacher education, and class size, are not associated with
increased effectiveness in Head Start. Together, observed inputs explain
about one-third of the variation in Head Start effectiveness across
experimental sites.
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