“…After identifying the initial sample of studies, I excluded studies if they did not meet at least one of the criteria. Several studies were conducted in preschool grades (He, Linden, & MacLeod, 2009;Jukes et al, 2006) or secondary grades (Angrist, Bettinger, Bloom, King, & Kremer, 2002;Blimpo, 2010;Liu et al, 2013). Some studies did not randomly assign units to treatment and control groups (Heyneman, Jamison, & Montenegro, 1984;Inamdar, 2004;Nitsaisook & Anderson, 1989;Rosas et al, 2003).…”