The results for kindergartners, meanwhile, were considerably more erratic; the effect of attending a private school for three years was a negative 13.9 percentile points.
Unfortunately, this is a hazardous generalization, given the fact that
the results for kindergartners were significantly different from those for the older students.
Not exact matches
In other words, Krueger and Zhu also now report consistently positive
results for African - Americans, regardless of how ethnicity is defined, even when
kindergartners are included in the analysis - as long as baseline scores (and only baseline scores) are taken into account in the statistical estimation of programmatic effects.
But since these analyses also introduce risks of bias (principally by including the
kindergartners for whom no baseline scores were available), the
results in Figure 2 are inferior to the
results provided in Figure 1.
In the absence of baseline scores, we don't know whether the findings
for kindergartners are genuine or simply the
result of errors in the administrative process.