Method. We used data from the ECLS-K:2011 to classify WM growth trajectories among 12,000 students between the spring of Kindergarten and spring of 4th grade using growth mixture modeling. WM was assessed using the numbers reversed task, in which children were asked to orally repeat increasingly longer strings of numbers in reverse order.
Results. Results revealed that almost a third of students (27.4%) displayed “low” WM scores during Kindergarten. Most of these students (22.4%) experienced steeper growth through the spring of 4th grade (labeled Improved), effectively catching up to their average-performing classmates. However, a small group of students (5.5%) retained a low WM score through 4th grade, which we labeled the Lowest performers. This group of students also had academic scores and behavioral ratings that were between one half and one full standard deviation lower than their Improved peers through 4th grade.
To better understand which students displayed such persistently poor WM, we conducted a logistic regression comparing these students to the Improved group. We found that the Lowest group was characterized by students who were Black (OR = 1.90), older at Kindergarten entry (OR = 1.09) and displayed poorer mathematics skill (OR = .91) during Kindergarten. Importantly, almost half of this group had a parent-reported disability (39%) and was receiving special education services during Kindergarten (40%), in contrast to the Improved group, of which 25% had a disability and only 14% received special education.
Conclusions. Results suggest that early disability is not only associated with poor early WM, but also predicts WM deficits that fail to recover with time. The strong association between WM deficits and disability may jointly suppress later academic performance and behavioral regulation. This finding has implications for prevention science, as it may help classify and subsequently target intervention toward students at risk of poor scholastic and behavioral outcomes during early schooling.