Classically, neuropsychological evaluation only estimates an individual’s performance at one time point. For example, working memory (WM) capacity is commonly determined in a single test session. However, recent research in WM plasticity and variability has suggested performance over several sessions/days might aid in evaluating children. Here, we explored four temporal properties of WM: WM measured once, as a mean over three days (multiple-session-baseline performance), variability over 8 weeks, and performance improvement over an 8-week WM training program. To examine independence we controlled for a single-session, multiple task WM assessment while predicting inattention and mathematics three years later (n = 178, mean age 80 months at training, 49 % boys). Our results showed improved prediction for mathematics from WM training improvement and variability, yet this was not the case for inattention. While the additional variance added was not substantial, our results indicate clinically relevant information present in these alternative WM measures.