“…Unfortunately, previous studies examining the effects of different service delivery models on achievement and nonachievement outcomes generally do not apply research designs that allow for causal inference (for reviews, see Assouline et al, 2015;Delcourt et al, 2007;Goldring, 1990;Steenbergen-Hu et al, 2016;Steenbergen-Hu & Moon, 2011;Vaughn et al, 1991). In studies where an experimental design was applied (e.g., Callahan et al, 2015;Gavin et al, 2009;Gubbels et al, 2014), the focus has been on the efficacy of a particular curriculum or enrichment program relative to the counterfactual of participation in a "business as usual" gifted program, not participation relative to nonparticipation. Critically, we do not have rigorous national estimates of the relationship between receiving gifted services at the elementary level and student academic and nonacademic outcomes.…”