As the previous discussion made clear, progress in narrowing the school readiness gap is generally measured in terms of how close children are to national norms. Closing the school readiness gap refers to bringing children to national norms on a specific outcome measure, such as a standardized literacy or math assessment. Using this yardstick, numerous studies have demonstrated that school readiness interventions make progress toward narrowing the gap but generally do not close the gap entirely. Some researchers have asked whether it is necessary to close the gap all the way before children begin school. Can disadvantaged children be kept in the running to participate in school even if they do not catch up to national norms? It is a tempting thought because, as we saw earlier, the size of the gap as children enter school is large and may be hard to close in one year before school. The question here is: Can school readiness research help identify a point that is sufficient to enable children to benefit fully from kindergarten and not continue to lose ground?
To investigate this question, we used longitudinal data from the ECLS-K, namely the scores on the reading test used from the fall of the kindergarten year through fifth grade (35,468 observations) to construct growth trajectories for children beginning kindergarten at varied literacy levels. If it were true that children entering school with scores at some point below the average score managed to catch up, we hypothesized that we would expect to see a different (i.e., slightly accelerated) growth trajectory for those children. In other words, we investigated the question of whether, at the start of kindergarten, children with lower than average literacy levels had faster rates of growth than children at higher literacy levels, moving their scores up to the average score. This would manifest itself as a steeper growth trajectory than the ones for both higher- and lower-performing peers. If this were the case, then helping to move children at least to this specified level before school might mean they could make somewhat greater gains than their peers in the early grades, and that the school experience itself would be instrumental in closing the gap.
Fall kindergarten Item Response Theory (IRT) scaled scores were used to sort children into deciles and then IRT scaled scores at four subsequent time-points were used to construct linear growth models for each decile. Exhibit 3 shows the mean growth trajectories for children from each of the ten deciles. For example, the curve at the bottom of the exhibit shows the mean Reading IRT scores over several time points, for the children whose scores taken in the fall of kindergarten were in the lowest 10 percent of the score distribution. The mean scores of these children were below the means of children from the higher deciles, as they progressed from kindergarten to first grade, on to grades 3 and 5. On average, the deciles move along nearly parallel tracks there is no group that breaks away and moves closer to another. In addition to the plots shown in Exhibit 3, we fitted linear growth curve models to the data. Consistent with the results shown in the plots, these models indicated that childrens scores from the fall kindergarten are highly predictive (p = <.0001) of their scores on the test in fifth grade. Furthermore, analysis of the ECLS-K data did not indicate that childrens rate of growth in literacy over the elementary school years was related to their literacy level at the start of kindergarten. Childrens average rate of growth in literacy through elementary school was effectively the same regardless of their fall kindergarten score. Children with high, moderate, and low literacy scores at the start of kindergarten all grew at the same rate, on average. At no level along the continuum of kindergarten starting points did the gap narrow over time between any deciles.
Of course, one possible reason why children in the lowest deciles do not catch up to others as a result of the school experience is that these predominantly low-income children may enter schools that are of lower quality than the schools their more advantaged peers enter. If it were true that low-income children could depend on having a high-quality kindergarten experience that supported the gains made as a result of an effective preschool intervention, the results might be different.
Looking at the ECLS-K data from a different perspective offers some additional insights into the reasons why children do not catch up. The reading test used for the ECLS-K actually was a composite of nine subtests drawn from existing tests. An examination of the decile growth curves for each of the subtests provides interesting insights and helps explain the overall growth pattern. Exhibits 4-11 show the decile growth curves for each of the subtests. As some have suggested, there are foundational skills (letter recognition, beginning sounds, ending sounds, sight words) that most children (except those in the lowest decile) have acquired by third grade, even if they lagged behind badly on entry to kindergarten. As the skill tested becomes more complex (understanding words in context), the time taken to catch up increases, and some of the deciles have not caught up by the end of fifth grade. Exhibits 7-10 show that, for the skills that are needed to interpret and understand what is read, which for most children do not manifest themselves at all until the end of the kindergarten year, the gaps between the deciles actually widen over time we are no longer looking at the parallel tracks that the overall reading score produces. Although children in the lower deciles do catch up to others on some skills, the delay may cost them the opportunity to develop adequately the skills that are important for school success.
These analyses demonstrate the relationship between early and later achievement scores and suggest ways in which early skills may be foundational for later skills. Findings also raise additional questions about whether it is adequate to narrow the school readiness gap or if the gap needs to be closed completely in order for children to benefit from later schooling. That is, it is clear that early delays in literacy skills can result in delays in the acquisition of more complex skills and leaves underperforming children at risk for school failure. The next step in exploring how to put children in the running for school success may be to identify the specific skills children need to benefit from learning opportunities in kindergarten (and later schooling) and the early childhood experiences that get them there.
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